Segmentation fault when clicking «Remove All Kern Pairs» in font with no kern pairs

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Arch Linux, fe7bc7c (development build—self-compiled)

Program received signal SIGSEGV, Segmentation fault.
0x00001555539a5c90 in free () from /usr/lib/libc.so.6
(gdb) bt
#0  0x00001555539a5c90 in free () at /usr/lib/libc.so.6
#1  0x00001555550e7c6a in KernClassFreeContents (kc=0x555556048a90) at ../fontforge/splineutil.c:6121
#2  0x00001555550e7fa1 in KernClassListFree (kc=0x555556048a90) at ../fontforge/splineutil.c:6170
#3  0x0000155554ec3ad6 in SFRemoveLookupSubTable (sf=0x555555f9be30, sub=0x55555603e950, remove_acs=0) at ../fontforge/lookups.c:1099
#4  0x0000155554ec3edd in SFRemoveLookup (sf=0x555555f9be30, otl=0x555555fdc030, remove_acs=0) at ../fontforge/lookups.c:1176
#5  0x0000155554e1e590 in FVRemoveKerns (fv=0x555555da56d0) at ../fontforge/autowidth.c:1146
#6  0x00005555556ff4a5 in FVMenuRemoveKern (gw=0x555555fae290, UNUSED_mi=0x555555fbe240, UNUSED_e=0x7fffffffcca0) at ../fontforgeexe/fontview.c:3463
#7  0x000055555587ec0a in gmenu_mouse (m=0x55555607fa80, event=0x7fffffffcca0) at ../gdraw/gmenu.c:948
#8  0x00005555558806cd in gmenu_eh (w=0x55555608d1e0, ge=0x7fffffffcca0) at ../gdraw/gmenu.c:1389
#9  0x0000555555860524 in _GGDKDraw_CallEHChecked (gw=0x55555608d1e0, event=0x7fffffffcca0, eh=0x5555558805f4 <gmenu_eh>) at ../gdraw/ggdkdraw.c:329
#10 0x0000555555862f47 in _GGDKDraw_DispatchEvent (event=0x555555bfd470, data=0x555555c17e10) at ../gdraw/ggdkdraw.c:1232
#11 0x00001555541bc8b4 in  () at /usr/lib/libgdk-3.so.0
#12 0x0000155554169904 in  () at /usr/lib/libgdk-3.so.0
#13 0x0000155553b4d3ae in g_main_context_dispatch () at /usr/lib/libglib-2.0.so.0
#14 0x0000155553b4f1c1 in  () at /usr/lib/libglib-2.0.so.0
#15 0x0000155553b4f201 in g_main_context_iteration () at /usr/lib/libglib-2.0.so.0
#16 0x0000555555865c72 in GGDKDrawEventLoop (gdisp=0x555555c17e10) at ../gdraw/ggdkdraw.c:2190
#17 0x0000555555851779 in GDrawEventLoop (gdisp=0x555555c17e10) at ../gdraw/gdraw.c:789
#18 0x0000555555815b29 in fontforge_main (argc=2, argv=0x7fffffffe0d8) at ../fontforgeexe/startui.c:1415
#19 0x00005555555aab29 in main (argc=2, argv=0x7fffffffe0d8) at ../fontforgeexe/main.c:33

Reproduction steps:

• Open T.ttf
• Metrics→Kern by Classes…
• New Lookup…
• Pair Positioning, kern, press OK
• Accept default subtable name 'kern' Horizontal Kerning lookup 0-1
• Add any kern pair, e.g. A a and V v
• Press «OK»
• In «Kern by Classes» dialog, press «Delete» on 'kern' Horizontal Kerning lookup 0-1
• Press «Done»
• Metrics→Remove All Kern Pairs
• Crash!