Problem: qsort may deref NULL pointer #711

Job	Run time
macos (tiny, macos-12)	1m 15s
linux (tiny, clang, native)	2m 3s
macos (tiny, macos-14)	50s
windows (HUGE, msvc, no, no, x64, stable)	6m 57s
linux (tiny, gcc, native)	2m 9s
macos (normal, macos-12)	8m 17s
windows (HUGE, mingw, yes, yes, x86, stable, yes)	9m 54s
macos (normal, macos-14)	4m 26s
linux (normal, clang, native)	5m 32s
macos (huge, macos-12)	15m 19s
macos (huge, macos-14)	14m 1s
windows (HUGE, msvc, no, yes, x86)	9m 46s
linux (normal, gcc, native)	6m 21s
linux (huge, clang, native)	9m 8s
windows (HUGE, mingw, yes, no, x64, yes)	9m 48s
linux (huge, gcc, native)	12m 2s
windows (NORMAL, msvc, yes, no, x86)	6m 52s
linux (tiny, clang, nogui)	1m 37s
windows (NORMAL, mingw, no, yes, x64)	8m 47s
linux (tiny, gcc, nogui)	2m 34s
windows (TINY, msvc, yes, yes, x64)	1m 54s
linux (normal, gcc, i386, ./src/shadow)	5m 53s
windows (TINY, mingw, no, no, x86)	2m 23s
linux (huge, gcc, uchar, testgui, true, dynamic)	10m 34s
linux (huge, clang, asan, 5.1)	16m 55s
linux (huge, gcc, unittests, true)	3m 38s
linux (normal, gcc, vimtags)	3m 25s
	3h 2m 20s

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