fix bug2

Author: lfffkh

pandas/core/construction.py

@@ -520,7 +520,6 @@ def sanitize_masked_array(data: ma.MaskedArray) -> np.ndarray:
             data.soften_mask()  # If the data is a Masked EA, directly soften the mask.
         else:
             dtype, fill_value = maybe_promote(data.dtype, np.nan)
-            dtype = cast(np.dtype, dtype)
             data = ma.asarray(data.astype(dtype, copy=True))
             data.soften_mask()  # set hardmask False if it was True
             data[mask] = fill_value