BUG: fix two missing array creation failure checks
BUG: fix missing memory allocation failure checks
BUG: fix use of capi without gil in ufunc.at

without a pointer to store the error NpyIter_ResetBasePointers uses
python errors to signal problems which requires the GIL.
Merge pull request #4267 from juliantaylor/fuzz-test

BUG: add more malloc failure checks