changes according to comments

Author: tp

pandas/core/groupby/generic.py

@@ -1208,9 +1208,7 @@ def count(self):
 
         mask = (ids != -1) & ~isna(val)
         ids = ensure_platform_int(ids)
-        minlength = ngroups or 0
-        if _np_version_under1p13 and minlength == 0:
-            minlength = None
+        minlength = ngroups or (None if _np_version_under1p13 else 0)
         out = np.bincount(ids[mask], minlength=minlength)
 
         return Series(out,