Add kwarg to new call-sites

Author: h-vetinari

pandas/core/reshape/merge.py

@@ -962,8 +962,8 @@ def _maybe_coerce_merge_keys(self):
             # object values are allowed to be merged
             elif ((lk_is_object and is_numeric_dtype(rk)) or
                   (is_numeric_dtype(lk) and rk_is_object)):
-                inferred_left = lib.infer_dtype(lk)
-                inferred_right = lib.infer_dtype(rk)
+                inferred_left = lib.infer_dtype(lk, skipna=False)
+                inferred_right = lib.infer_dtype(rk, skipna=False)
                 bool_types = ['integer', 'mixed-integer', 'boolean', 'empty']
                 string_types = ['string', 'unicode', 'mixed', 'bytes', 'empty']