Fix bug pandas-dev#50153

Instead of raising a KeyError in case a key is available in a level
but not found with the combination of previous keys an empty array
is returned.

Author: fwitte

pandas/core/indexes/multi.py

@@ -3288,7 +3288,7 @@ def _to_bool_indexer(indexer) -> npt.NDArray[np.bool_]:
             else:
                 indexer &= lvl_indexer
                 if not np.any(indexer) and np.any(lvl_indexer):
-                    raise KeyError(seq)
+                    return np.array([], dtype=np.intp)
 
         # empty indexer
         if indexer is None: