bug fix: CHOLMOD/Supernodal #451

Job	Run time
macos	8m 50s
mingw (MINGW64)	9m 41s
msvc (with OpenMP)	7m 27s
mingw (MINGW32)	10m 52s
msvc (without OpenMP)	6m 12s
mingw (CLANG64)	1h 0m 13s
ubuntu (gcc with CUDA with OpenMP)	5m 44s
mingw (CLANG32)	1h 5m 6s
ubuntu (gcc without CUDA with OpenMP)	3m 45s
ubuntu (clang with CUDA with OpenMP)	6m 1s
ubuntu (clang without CUDA with OpenMP)	3m 4s
ubuntu (gcc without CUDA without OpenMP)	2m 52s
	3h 9m 47s

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