--- a/hgext3rd/topic/__init__.py	Wed May 08 15:57:54 2019 +0800
+++ b/hgext3rd/topic/__init__.py	Wed May 08 16:00:34 2019 +0800
@@ -735,8 +735,8 @@
     ct = repo.currenttopic
     if clear:
         if ct:
-            empty = stack.stack(repo, topic=ct).changesetcount == 0
-            if empty:
+            st = stack.stack(repo, topic=ct)
+            if not st:
                 ui.status(_('clearing empty topic "%s"\n') % ct)
         return _changecurrenttopic(repo, None)
 
@@ -1234,8 +1234,8 @@
             if t and t != ot:
                 repo.ui.status(_("switching to topic %s\n") % t)
             if ot and not t:
-                empty = stack.stack(repo, topic=ot).changesetcount == 0
-                if empty:
+                st = stack.stack(repo, topic=ot)
+                if not st:
                     repo.ui.status(_('clearing empty topic "%s"\n') % ot)
         elif ist0:
             repo.ui.status(_("preserving the current topic '%s'\n") % ot)

--- a/hgext3rd/topic/stack.py	Wed May 08 15:57:54 2019 +0800
+++ b/hgext3rd/topic/stack.py	Wed May 08 16:00:34 2019 +0800
@@ -248,9 +248,6 @@
         label = 'topic.active'
 
     st = stack(repo, branch, topic)
-    empty = False
-    if st.changesetcount == 0:
-        empty = True
     if topic is not None:
         fm.plain(_('### topic: %s')
                  % ui.label(topic, label),
@@ -281,7 +278,7 @@
             fm.plain('%d behind' % st.behindcount, label='topic.stack.summary.behindcount')
     fm.plain('\n')
 
-    if empty:
+    if not st:
         fm.plain(_("(stack is empty)\n"))
 
     st = stack(repo, branch=branch, topic=topic)