TST: be robust to clip shapes in dev numpy

closes pandas-dev#19976

Author: jreback

pandas/core/generic.py

@@ -5602,9 +5602,9 @@ def clip(self, lower=None, upper=None, axis=None, inplace=False,
         # GH 17276
         # numpy doesn't like NaN as a clip value
         # so ignore
-        if np.any(pd.isnull(lower)):
+        if np.any(isna(np.asarray(lower).ravel())):
             lower = None
-        if np.any(pd.isnull(upper)):
+        if np.any(isna(np.asarray(upper).ravel())):
             upper = None
 
         # GH 2747 (arguments were reversed)