fix segfault #263

Job	Run time
macos (tiny)	2m 9s
macos (normal)	8m 25s
macos (huge)	16m 47s
windows (HUGE, msvc, no, no, x64)	4m 36s
windows (HUGE, mingw, yes, yes, x86, yes)	7m 24s
windows (HUGE, msvc, no, yes, x86)	6m 36s
windows (HUGE, mingw, yes, no, x64, yes)	7m 35s
windows (NORMAL, msvc, yes, no, x86)	8m 21s
windows (NORMAL, mingw, no, yes, x64)	10m 41s
windows (TINY, msvc, yes, yes, x64)	51s
windows (TINY, mingw, no, no, x86)	2m 25s
linux (tiny, clang, none)	1m 53s
linux (tiny, gcc, none)	1m 26s
linux (normal, clang, none)	8m 15s
linux (normal, gcc, none)	8m 10s
linux (huge, clang, none)	9m 6s
linux (huge, gcc, none)	8m 29s
linux (tiny, clang, nogui)	1m 34s
linux (tiny, gcc, nogui)	1m 26s
linux (huge, gcc, testgui, true, true)	8m 10s
linux (huge, clang, asan)	19m 50s
linux (huge, gcc, unittests, true)	2m 20s
linux (normal, gcc, vimtags)	1m 28s
	2h 27m 57s

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