Fix Vertex entity index4 parsing #5247

Job	Run time
mips32-big-endian	10m 19s
macOS	12m 27s
mingw	36m 14s
vs2019-ninja	5m 47s
mingw-cmake	4m 16s
ppc64-big-endian	8m 23s
linux (--enable-release)	36m 4s
linux (CFLAGS="-O1 -fno-omit-frame-pointer -fsanitize=address -fno-var-tracking" --disable-bindin...	3m 54s
linux-cmake	2m 7s
linux (CFLAGS="-O2 -fno-omit-frame-pointer -fsanitize=undefined -fno-var-tracking" --disable-bind...	9m 7s
linux (--enable-gcov --disable-bindings --disable-docs CFLAGS="-O0 -g")	5m 22s
linux (--disable-write --disable-docs)	5m 8s
vs2019	7m 17s
linux (CC="clang")	4m 26s
linux (--enable-debug)	2m 3s
linux (--host=i686-linux-gnu --disable-bindings --disable-docs)	4m 54s
	2h 37m 48s

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