Reopening - dade2a74c70808f7b4bb86604e4ba11004946cbe introduces crashes when zooming out 9x and looking on the side of level 0.

#0  0x00005555555c7340 in insert_obstacles_into_blitting_list (mask=mask@entry=4076) at view.c:436
#1  0x00005555555c756c in set_up_ordered_blitting_list (mask=mask@entry=4076) at view.c:1246
#2  0x00005555555cb6a9 in AssembleCombatPicture (mask=<optimized out>) at view.c:1836
#3  0x00005555555d337a in leveleditor_display () at lvledit/lvledit_display.c:299
#4  0x00005555555cf79d in LevelEditor () at lvledit/lvledit.c:287
#5  0x00005555555714ad in main (argc=2, argv=0x7fffffffdb38) at main.c:189
#6  0x00007ffff7571ee3 in __libc_start_main () from /usr/lib/libc.so.6
#7  0x000055555557156e in _start () at main.c:174