need to refresh ui after resetting completion state

Author: randy3k

prompt_toolkit/buffer.py

@@ -1476,6 +1476,7 @@ def add_completion(completion):
  # When there are no completions, reset completion state anyway.
  if not completions:
  self.complete_state = None
+ self.on_completions_changed.fire()
  return
 
  # Select first/last or insert common part, depending on the key