plugin: fix crash on parsing empty command

edmond/plugin.py

@@ -101,6 +101,8 @@ class Plugin:
     def should_handle_command(self, message, no_content=False):
         """Store Command in object and return True if it should handle it."""
         command = self.parse_command(message, no_content=no_content)
+        if not command:
+            return False
         commands = self.config.get("commands", [])
         if (
             any(command.ident == c for c in commands) or