[Bug] i.vi: segmentation fault with non-existing input map(s)

[neteler]

Describe the bug

When using i.vi with non-existing input map(s) it segfaults:

# works
GRASS nc_spm_08_grass7/user1:~ > g.region raster=lsat7_2002_30

GRASS nc_spm_08_grass7/user1:~ > i.vi red=lsat7_2002_30 nir=lsat7_2002_40 viname=ndvi output=lsat7_2002.ndvi
 100%

# fails
GRASS nc_spm_08_grass7/user1:~ > i.vi green=not_there nir=non_existing viname=ndwi output=ndwi
Segmentation fault (core dumped)

To Reproduce

GRASS nc_spm_08_grass7/user1:~ > gdb i.vi
GNU gdb (GDB) Fedora 10.1-2.fc33
...
Reading symbols from i.vi...
(gdb) r green=not_there nir=non_existing viname=ndwi output=ndwi
Starting program: /home/mneteler/software/grass_master/dist.x86_64-pc-linux-gnu/bin/i.vi green=not_there nir=non_existing viname=ndwi output=ndwi
Missing separate debuginfos, use: dnf debuginfo-install glibc-2.32-4.fc33.x86_64
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7f5720d in G_name_is_fully_qualified (fullname=0x0, name=0x7fffffffc680 "", mapset=0x7fffffffc780 "")
    at nme_in_mps.c:45
45	    for (p = fullname; *p; p++)
Missing separate debuginfos, use: dnf debuginfo-install SuperLU-5.2.1-14.fc33.x86_64 armadillo-10.2.0-1.fc33.x86_64
...
(gdb) bt full
#0  0x00007ffff7f5720d in G_name_is_fully_qualified (fullname=0x0, name=0x7fffffffc680 "", mapset=0x7fffffffc780 "")
    at nme_in_mps.c:45
        p = 0x0
        q = 0x7ffff7faea56 <init+613> "\307\005\030\240\001"
#1  0x00007ffff7f573a9 in G_unqualified_name (name=0x0, mapset=0x406bcf "", xname=0x7fffffffc680 "", xmapset=0x7fffffffc780 "")
    at nme_in_mps.c:137
No locals.
#2  0x00007ffff7fb0718 in Rast__open_old (name=0x0, mapset=0x406bcf "") at open.c:172
        fcb = 0x480ab0
        cell_fd = 32767
        fd = 48
        cell_dir = 0x7fffffffc780 ""
        r_name = 0x7fffffffc6b0 "\340\334G"
        r_mapset = 0x7ffffbad8001 <error: Cannot access memory at address 0x7ffffbad8001>
        cellhd = {format = 0, compressed = 0, rows = 338460416, rows3 = -2097709812, cols = 0, cols3 = 0, depths = 0, proj = 0, 
          zone = 4710752, ew_res = 2.3242428990438929e-317, ew_res3 = 0, ns_res = 2.3274207292779438e-317, 
          ns_res3 = 3.4090529563046012e-322, tb_res = 6.9533489704878039e-310, north = -nan(0xfffff00000000), 
          south = 6.9533558071203878e-310, east = 2.3268752808049351e-317, west = 6.9533490506244612e-310, top = 0, bottom = 0}
        CELL_nbytes = 0
        INTERN_SIZE = 16
        reclass_flag = 4721272
        MAP_NBYTES = 32767
        MAP_TYPE = 0
        reclass = {name = 0x480ab0 "8", mapset = 0x480ab0 "8", type = 4721152, num = 0, min = 4721328, max = 0, table = 0x480ab1}
        xname = "\000\310G\000\000\000\000\000\340\023\331\367", '\000' <repeats 12 times>, "\220\307\377\377\377\177\000\000\020\335G\000\000\000\000\000\200\307\377\377\377\177\000\000\340\334G\000\000\000\000\000\200\307\377\377\377\177\000\000\070\310\377\377\377\177\000\000\340\334G\000\000\000\000\000\001", '\000' <repeats 15 times>, "@\336G\000\000\000\000\000\220\307\377\377\377\177\000\000\020\335G\000\000\000\000\000G3\300\367\377\177\000\000\000\000\000\000\000\000\000\000S\364\367\367\377\177\000\000b\364\367\367\377\177\000\000\326\307\377\377\377\177\000\000\060\310\377\377\377\177\000\000\224\274\365\367\377\177", '\000' <repeats 11 times>, "\177,\024\f}\367\202\000\000\000\000\000\000\000\000"...
        xmapset = "\000\000_US\000\000\000\344\250\300\367\377\177\000\000LC_MESSA\260\345G\000\000\000\000\000\340\307\377\377\377\177\000\000\360a@\000\000\000\000\000\030b@\000\000\000\000\000\260\361\370\367\377\177\000\000\340\307\377\377\377\177\000\000{E\367\367\377\177\000\000\na@", '\000' <repeats 13 times>, "\340\310\377\377\377\177\000\000%\233\362\367\377\177\000\000\000\000\000\000\000\000\000\000Qh@", '\000' <repeats 17 times>, "\005\000\000\000\220\307\377\377\377\177\000\000\000\000\000\000\377\177\000\000\020\335G\000\000\000\000\000\060\vH\000\000\000\000\000Qh@\000\000\000\000\000\002\000\000\000\000\000\000\000 \025\331\367\377\177\000\000\000\000\000\000\000\000\000\000"...
        gdal = 0x480ab1
        vrt = 0x480ab1
#3  0x00007ffff7fb06a8 in Rast_open_old (name=0x0, mapset=0x406bcf "") at open.c:114
        fd = 0
#4  0x00000000004039de in main (argc=5, argv=0x7fffffffcd38) at main.c:294
        nrows = 0
        ncols = 4695936
        row = 0
        col = 17
        viflag = 0x480b30 "ndwi"
        desc = 0x47fc40 "arvi;Atmospherically Resistant Vegetation Index;dvi;Difference Vegetation Index;evi;Enhanced Vegetation Index;evi2;Enhanced Vegetation Index 2;gvi;Green Vegetation Index;gari;Green Atmospherically Res"...
        module = 0x7ffff7f8ef08 <state+40>
        opt = {viname = 0x47e0a0, red = 0x47eb20, nir = 0x47ebc0, green = 0x47ec80, blue = 0x47ed40, chan5 = 0x47e1f0, 
          chan7 = 0x47e2b0, sl_slope = 0x47e370, sl_int = 0x47e430, sl_red = 0x47e4f0, bits = 0x47e5b0, 
          output = 0x7ffff7f8ef68 <state+136>}
        history = {fields = {0x46 <error: Cannot access memory at address 0x46>, 0x47a7c0 "nc_spm_08_grass7", 
            0x13 <error: Cannot access memory at address 0x13>, 0x13 <error: Cannot access memory at address 0x13>, 0x0, 
            0x47 <error: Cannot access memory at address 0x47>, 0x7fffffffcaa0 "VP ENT HDR", 
            0xa <error: Cannot access memory at address 0xa>}, nlines = 1159745622, lines = 0x5244}
        colors = {version = -136775072, shift = 5.6619923013406854e-321, invert = 0, is_float = 0, null_set = 32, 
          null_red = 0 '\000', null_grn = 0 '\000', null_blu = 0 '\000', undef_set = -13504, undef_red = 255 '\377', 
          undef_grn = 127 '\177', undef_blu = 0 '\000', fixed = {rules = 0x7ffff7d8fa00 <main_arena>, n_rules = 1056, lookup = {
              red = 0x410 <error: Cannot access memory at address 0x410>, 
              grn = 0x42 <error: Cannot access memory at address 0x42>, blu = 0x6e <error: Cannot access memory at address 0x6e>, 
              set = 0x77 <error: Cannot access memory at address 0x77>, nalloc = -138057399, active = 32767}, fp_lookup = {
              vals = 0x1b, rules = 0x1, nalloc = 64, active = 0}, min = 3.4584595208887258e-323, max = 0}, modular = {
            rules = 0x410, n_rules = 64, lookup = {red = 0x50 <error: Cannot access memory at address 0x50>, 
              grn = 0x440 <error: Cannot access memory at address 0x440>, 
              blu = 0x10 <error: Cannot access memory at address 0x10>, 
              set = 0x4000000042 <error: Cannot access memory at address 0x4000000042>, nalloc = 0, active = 0}, fp_lookup = {
              vals = 0x0, rules = 0x2, nalloc = 93, active = 119}, min = 2.6312747813404099e-312, max = 3.9525251667299724e-322}, 
          cmin = 3.7967956751608114e-319, cmax = 6.953349050243833e-310, organizing = 4216189}
        result = 0x480b50 "ndwi"
        infd_redchan = 0
        infd_nirchan = 0
        infd_greenchan = 17
        infd_bluechan = 0
        infd_chan5chan = 0
        infd_chan7chan = 0
        outfd = 0
        bluechan = 0x0
        greenchan = 0x480a00 "not_there"
        redchan = 0x0
        nirchan = 0x480b10 "non_existing"
        chan5chan = 0x0
        chan7chan = 0x0
        inrast_redchan = 0x8
        inrast_nirchan = 0x11
        inrast_greenchan = 0x0
        inrast_bluechan = 0x43
        inrast_chan5chan = 0x7fffffffca00
        inrast_chan7chan = 0x5
        outrast = 0x454c5954534d4944
        data_type_redchan = 66
        data_type_nirchan = 65
        data_type_greenchan = 0
        data_type_bluechan = -13904
        data_type_chan5chan = 32767
        data_type_chan7chan = 5
        msavip1 = 0
        msavip2 = 2.22601511e+11
        msavip3 = 1.17709071e-43
        dnbits = 8
        val1 = 0
        val2 = 4695904

Expected behavior

The module should print a fatal error that the map isn't there and end.

System description (please complete the following information):

• Fedora 33
• GRASS GIS 7.8 and 7.9

g.version -rge
version=7.9.dev
date=2021
revision=3a50170e7
build_date=2021-02-16
build_platform=x86_64-pc-linux-gnu
build_off_t_size=8
libgis_revision=d79d6ff90
libgis_date=2021-02-13T16:23:10+00:00
proj=6.3.2
gdal=3.1.4
geos=3.8.1
sqlite=3.34.1

Additional context
Add any other context about the problem here.