send_pm_if_empty_stream: Clean up unnecessary nesting.

This has no functional changes.

zerver/lib/actions.py

@@ -1109,7 +1109,9 @@ def send_pm_if_empty_stream(sender, stream, stream_name, realm):
     if sender.realm.is_zephyr_mirror_realm or sender.realm.deactivated:
         return
 
-    if sender.is_bot and sender.bot_owner is not None:
+    if not sender.is_bot or sender.bot_owner is None:
+        return
+
     # Don't send these notifications for cross-realm bot messages
     # (e.g. from EMAIL_GATEWAY_BOT) since the owner for
     # EMAIL_GATEWAY_BOT is probably the server administrator, not
@@ -1117,21 +1119,23 @@ def send_pm_if_empty_stream(sender, stream, stream_name, realm):
     if sender.realm != realm:
         return
 
-        if stream:
+    if stream is not None:
         num_subscribers = stream.num_subscribers()
+        if num_subscribers > 0:
+            return
 
-        if stream is None or num_subscribers == 0:
-            # Warn a bot's owner if they are sending a message to a stream
-            # that does not exist, or has no subscribers
     # We warn the user once every 5 minutes to avoid a flood of
     # PMs on a misconfigured integration, re-using the
     # UserProfile.last_reminder field, which is not used for bots.
     last_reminder = sender.last_reminder
     waitperiod = datetime.timedelta(minutes=UserProfile.BOT_OWNER_STREAM_ALERT_WAITPERIOD)
-            if not last_reminder or timezone.now() - last_reminder > waitperiod:
+    if last_reminder and timezone.now() - last_reminder <= waitperiod:
+        return
+
     if stream is None:
         error_msg = "that stream does not yet exist. To create it, "
-                elif num_subscribers == 0:
+    else:
+        # num_subscribers == 0
         error_msg = "there are no subscribers to that stream. To join it, "
 
     content = ("Hi there! We thought you'd like to know that your bot **%s** just "