Null pointer dereference in decompileINCR_DECR (util/decompile.c:1597)

[cutedog2012]

Hi, I found a null pointer dereference in function decompileINCR_DECR at util/decompile.c:1597 on the latest master (5009802).
The details are as follows:

`==17334==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000010 (pc 0x0000004161cf bp 0x7fff4e703770 sp 0x7fff4e703730 T0)
#0 0x4161ce in decompileINCR_DECR /home/zyn/Lollycode/tested/libming0.4.8/poc-libming-master/util/decompile.c:1597
#1 0x41ee50 in decompileAction /home/zyn/Lollycode/tested/libming0.4.8/poc-libming-master/util/decompile.c:3315
#2 0x41f37d in decompileActions /home/zyn/Lollycode/tested/libming0.4.8/poc-libming-master/util/decompile.c:3494
#3 0x41f4b3 in decompile5Action /home/zyn/Lollycode/tested/libming0.4.8/poc-libming-master/util/decompile.c:3517
#4 0x40bb42 in outputSWF_DOACTION /home/zyn/Lollycode/tested/libming0.4.8/poc-libming-master/util/outputscript.c:1551
#5 0x40e171 in outputBlock /home/zyn/Lollycode/tested/libming0.4.8/poc-libming-master/util/outputscript.c:2083
#6 0x40f1c7 in readMovie /home/zyn/Lollycode/tested/libming0.4.8/poc-libming-master/util/main.c:281
#7 0x40f8fc in main /home/zyn/Lollycode/tested/libming0.4.8/poc-libming-master/util/main.c:354
#8 0x7fb88a77182f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)
#9 0x401998 in _start (/home/zyn/Lollycode/tested/libming0.4.8/poc-libming-master/util/swftocxx+0x401998)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV /home/zyn/Lollycode/tested/libming0.4.8/poc-libming-master/util/decompile.c:1597 decompileINCR_DECR
==17334==ABORTING
`

I debugged and got the following details at util/decompile.c:1597:
`(gdb) p regs
$3 = {0x0, 0x60300000ed70, 0x60300000ed40, 0x60300000ed10, 0x60300000ece0, 0x0 <repeats
251 times>}
(gdb) p actions[n+1].SWF_ACTIONSTOREREGISTER.Register
$4 = 0 '\000'
(gdb) p regs[actions[n+1].SWF_ACTIONSTOREREGISTER.Register]
$5 = (struct SWF_ACTIONPUSHPARAM *) 0x0
(gdb) p regs[actions[n+1].SWF_ACTIONSTOREREGISTER.Register]->Type
Cannot access memory at address 0x10
(gdb) s

Program received signal SIGSEGV, Segmentation fault.
0x00000000004161cf in decompileINCR_DECR (n=9, actions=0x61e00000f080, maxn=30, is_incr
=0) at decompile.c:1597
`
Because regs[actions[n+1].SWF_ACTIONSTOREREGISTER.Register] is null, there exists a null pointer dereference when accessing regs[actions[n+1].SWF_ACTIONSTOREREGISTER.Register]->Type.

POC file:
poc-1597.zip