changes according to comments

Author: tp

pandas/core/groupby/generic.py

@@ -1208,7 +1208,7 @@ def count(self):
 
         mask = (ids != -1) & ~isna(val)
         ids = ensure_platform_int(ids)
-        minlength = ngroups or 0
+        minlength = ngroups
         if _np_version_under1p13 and minlength == 0:
             minlength = None
         out = np.bincount(ids[mask], minlength=minlength)