load_icon_themes_from_dir: never reuse GKeyFile object

[mtasaka]

As written on:
https://developer.gnome.org/glib/stable/glib-Key-value-file-parser.html#g-key-file-load-from-file
an empty GKeyFile object must be passed to g_key_file_load_from_file .

========================================================
Again, like lxde/lxsession#27 , on Fedora 34 (using glib2-2.68.0-1.fc34.x86_64), lxappearance immediately segfaults like:

[tasaka1@localhost x86_64]$ gdb --args lxappearance 
GNU gdb (GDB) Fedora 10.1-10.fc34

(gdb) r
Starting program: /usr/bin/lxappearance 

Thread 1 "lxappearance" received signal SIGSEGV, Segmentation fault.
g_key_file_locale_is_interesting (locale=0x55555584b650 "af", key_file=0x5555558034f0) at ../glib/gkeyfile.c:1241
1241	  for (i = 0; key_file->locales[i] != NULL; i++)
Missing separate debuginfos, use: dnf debuginfo-install adwaita-gtk2-theme-3.28-12.fc34.x86_64 atk-2.36.0-3.fc34.x86_64 bzip2-libs-1.0.8-6.fc34.x86_64 cairo-1.17.4-3.fc34.x86_64 fontconfig-2.13.93-5.fc34.x86_64 freetype-2.10.4-3.fc34.x86_64 fribidi-1.0.10-4.fc34.x86_64 gdk-pixbuf2-2.42.2-2.fc34.x86_64 graphite2-1.3.14-7.fc34.x86_64 harfbuzz-2.7.4-3.fc34.x86_64 libXau-1.0.9-6.fc34.x86_64 libXcomposite-0.4.5-5.fc34.x86_64 libXcursor-1.2.0-5.fc34.x86_64 libXdamage-1.1.5-5.fc34.x86_64 libXext-1.3.4-6.fc34.x86_64 libXfixes-5.0.3-14.fc34.x86_64 libXi-1.7.10-6.fc34.x86_64 libXinerama-1.1.4-8.fc34.x86_64 libXrandr-1.5.2-6.fc34.x86_64 libXrender-0.9.10-14.fc34.x86_64 libblkid-2.36.2-1.fc34.x86_64 libbrotli-1.0.9-4.fc34.x86_64 libdatrie-0.2.13-1.fc34.x86_64 libffi-3.1-28.fc34.x86_64 libmount-2.36.2-1.fc34.x86_64 libpng-1.6.37-8.fc34.x86_64 libselinux-3.2-1.fc34.x86_64 libthai-0.1.28-6.fc34.x86_64 libxcb-1.13.1-7.fc34.x86_64 libxml2-2.9.10-10.fc34.x86_64 pcre-8.44-3.fc34.1.x86_64 pixman-0.40.0-3.fc34.x86_64 xz-libs-5.2.5-5.fc34.x86_64 zlib-1.2.11-24.fc34.x86_64
(gdb) bt
#0  g_key_file_locale_is_interesting (locale=0x55555584b650 "af", key_file=0x5555558034f0) at ../glib/gkeyfile.c:1241
#1  g_key_file_parse_key_value_pair (error=0x7fffffffcc40, length=<optimized out>, line=<optimized out>, key_file=0x5555558034f0) at ../glib/gkeyfile.c:1427
#2  g_key_file_parse_line (error=0x7fffffffcc38, length=<optimized out>, line=<optimized out>, key_file=0x5555558034f0) at ../glib/gkeyfile.c:1273
#3  g_key_file_flush_parse_buffer (key_file=key_file@entry=0x5555558034f0, error=error@entry=0x7fffffffcca0) at ../glib/gkeyfile.c:1542
#4  0x00007ffff76d6cdc in g_key_file_parse_data
    (key_file=0x5555558034f0, data=0x7fffffffcda0 "[Icon Theme]\nName=Mist\nName[af]=Mis\nName[ar]=غشى\nName[as]=কুঁৱলী\nName[ast]=Ñeblina\nName[az]=Çən\nName[be]=Туман\nName[be@latin]=Mist\nName[bg]=Мъгла\nName[bn]=কুয়া", <incomplete sequence \340\246>..., length=4096, error=0x7fffffffcd08) at ../glib/gkeyfile.c:1496
#5  0x00007ffff76d6f59 in g_key_file_load_from_fd (key_file=key_file@entry=0x5555558034f0, fd=fd@entry=9, flags=flags@entry=G_KEY_FILE_NONE, error=error@entry=0x7fffffffddf0)
    at ../glib/gkeyfile.c:857
#6  0x00007ffff76d7054 in g_key_file_load_from_file (key_file=0x5555558034f0, file=<optimized out>, flags=G_KEY_FILE_NONE, error=0x0) at ../glib/gkeyfile.c:924
#7  0x000055555555d55e in load_icon_themes_from_dir (base_dir=0x55555566d330 "/usr/share/icons", theme_dir=0x55555566d330 "/usr/share/icons", kf=0x5555558034f0)
    at /usr/src/debug/lxappearance-0.6.3-12.100.D20200807gitd132fdd8.fc35.x86_64/lxappearance/src/icon-theme.c:84
#8  0x000055555555d892 in load_icon_themes () at /usr/src/debug/lxappearance-0.6.3-12.100.D20200807gitd132fdd8.fc35.x86_64/lxappearance/src/icon-theme.c:125
#9  icon_theme_init (b=<optimized out>) at /usr/src/debug/lxappearance-0.6.3-12.100.D20200807gitd132fdd8.fc35.x86_64/lxappearance/src/icon-theme.c:247
#10 0x000055555555abaf in main (argc=<optimized out>, argv=<optimized out>)
    at /usr/src/debug/lxappearance-0.6.3-12.100.D20200807gitd132fdd8.fc35.x86_64/lxappearance/src/lxappearance.c:688

[mtasaka]

Well, https://gitlab.gnome.org/GNOME/glib/-/issues/2361 says glib side fixed this issue on 2.68.1. I will check this later.

[mtasaka]

I don't think this is needed any more.