decrypt_message: don't always send heartbeat

Signed-off-by: Maxime “pep” Buquet <pep@bouah.net>

slixmpp_omemo/__init__.py

@@ -643,7 +643,7 @@ class XEP_0384(BasePlugin):
         finally:
             asyncio.ensure_future(self._publish_bundle())
 
-        if self.auto_heartbeat:
+        if self.auto_heartbeat and self.should_heartbeat():
             msg = self.make_heartbeat(jid)
             msg.send()