Backport PR pandas-dev#29243: Follow up PR: pandas-dev#28097 Simplify branch statement (pandas-dev#31689)

Co-authored-by: proost <[email protected]>

Author: meeseeksmachine

pandas/core/indexes/multi.py

@@ -1270,10 +1270,10 @@ def _get_grouper_for_level(self, mapper, level):
             # on the output of a groupby doesn't reflect back here.
             level_index = level_index.copy()
 
-        if len(level_index):
-            grouper = level_index.take(codes)
-        else:
+        if level_index._can_hold_na:
             grouper = level_index.take(codes, fill_value=True)
+        else:
+            grouper = level_index.take(codes)
 
         return grouper, codes, level_index