NULL pointer dereference in iwgif_record_pixel

[bestshow]

on ImageWorsener 1.3.0

#imagew $FILE out.png
SEGV on unknown address 0x000000000000 (pc 0x0000005881eb bp 0x7fff07bfd4b0 sp 0x7fff07bfd310 T0)
==37476==The signal is caused by a READ memory access.
==37476==Hint: address points to the zero page.
#0 0x5881ea in iwgif_record_pixel /home/haojun/Downloads/testopensourcecode/imageworsener-master/src/imagew-gif.c:223:5
#1 0x587765 in lzw_emit_code /home/haojun/Downloads/testopensourcecode/imageworsener-master/src/imagew-gif.c:312:3
#2 0x5870ea in lzw_process_code /home/haojun/Downloads/testopensourcecode/imageworsener-master/src/imagew-gif.c:376:3
#3 0x586dd0 in lzw_process_bytes /home/haojun/Downloads/testopensourcecode/imageworsener-master/src/imagew-gif.c:433:9
#4 0x5840d0 in iwgif_read_image /home/haojun/Downloads/testopensourcecode/imageworsener-master/src/imagew-gif.c:669:7
#5 0x582413 in iwgif_read_main /home/haojun/Downloads/testopensourcecode/imageworsener-master/src/imagew-gif.c:724:9
#6 0x581bdd in iw_read_gif_file /home/haojun/Downloads/testopensourcecode/imageworsener-master/src/imagew-gif.c:773:6
#7 0x566c04 in iw_read_file_by_fmt /home/haojun/Downloads/testopensourcecode/imageworsener-master/src/imagew-allfmts.c:61:12
#8 0x519fbe in iwcmd_run /home/haojun/Downloads/testopensourcecode/imageworsener-master/src/imagew-cmd.c:1191:6
#9 0x516623 in iwcmd_main /home/haojun/Downloads/testopensourcecode/imageworsener-master/src/imagew-cmd.c:3018:7
#10 0x5164f1 in main /home/haojun/Downloads/testopensourcecode/imageworsener-master/src/imagew-cmd.c:3067:9
#11 0x7f47a59a8b34 in __libc_start_main (/lib64/libc.so.6+0x21b34)
#12 0x41bbeb in _start (/home/haojun/Downloads/testopensourcecode/imageworsener-master/imagew+0x41bbeb)

SEGV /home/haojun/Downloads/testopensourcecode/imageworsener-master/src/imagew-gif.c:223:5 in iwgif_record_pixel

testcase:
https://github.com/bestshow/p0cs/blob/master/1016-NULL-ptr-imagew-gif_223_5

Author: ADLab of Venustech

[jsummers]

Should be fixed by commit dc74009