Cleaned up comment

Author: rhshadrach

pandas/core/groupby/groupby.py

@@ -2514,7 +2514,7 @@ def _get_cythonized_result(
             key = base.OutputKey(label=name, position=idx)
             output[key] = result
 
-        # Check error_msg so we don't raise on an frame/series with no rows
+        # error_msg is "" on an frame/series with no rows or columns
         if len(output) == 0 and error_msg != "":
             raise TypeError(error_msg)