BUG: Dataframe constructor fails when given dict with None value pandas-dev#14381

Author: shawnheide

pandas/core/series.py

@@ -2897,6 +2897,9 @@ def _try_cast(arr, take_fast_path):
 
         subarr = _possibly_cast_to_datetime(subarr, dtype)
 
+    elif data is None:
+        subarr = np.array(np.nan)
+
     else:
         subarr = _try_cast(data, False)