Reorder tests in maybe_downcast_numeric

pandas/core/dtypes/cast.py

@@ -357,15 +357,13 @@ def trans(x):
             # if we don't have any elements, just astype it
             return trans(result).astype(dtype)
 
-        # do a test on the first element, if it fails then we are done
-        r = result.ravel()
-        arr = np.array([r[0]])
-
-        if isna(arr).any():
-            # if we have any nulls, then we are done
-            return result
-
-        elif not isinstance(r[0], (np.integer, np.floating, int, float, bool)):
+        if isinstance(result, np.ndarray):
+            element = result[0]
+        else:
+            element = result.iloc[0]
+        if isinstance(element, np.ndarray):
+            element = element.ravel()[0]
+        if not isinstance(element, (np.integer, np.floating, int, float, bool)):
             # a comparable, e.g. a Decimal may slip in here
             return result