BUG: Fix memory leak in ndarray construction from strings (gh-2927)
Merge pull request #2928 from mwiebe/string_init_memleak

BUG: Fix memory leak in ndarray construction from strings (gh-2927)
BUG: Fix segfault in np.result_type for None input.

Makes behavior identical to np.dtype(None), which fits to how
the function works.
Merge pull request #2933 from seberg/result_type-segfault

BUG: Fix segfault in np.result_type for None input.