BUG: MultiIndex.putmask

[jbrockmendel]

left = pd.MultiIndex.from_tuples([(np.nan, 6), (np.nan, 6), ("a", 4)])
right = pd.MultiIndex.from_tuples([("a", 1), ("a", 1), ("d", 1)])
mask = np.array([True, True, False])

result = left.putmask(mask, right)
>>> result
[...]
IndexError: list index out of range

The result here somehow ended up with len(result.levels) == 0

[simonjayhawkins]

on 1.2.5 this raises TypeError: Expected tuple, got MultiIndex