Don't raise error when there are no argument completions

Author: alexrudd2

pymodbus/repl/client/completer.py

@@ -130,6 +130,8 @@ def get_completions(self, document, complete_event):
 
             if " " in text:
                 command = self.arg_completions(words, word_before_cursor)
+                if not command:
+                    return
                 commands = list(command.get_completion())
                 commands = list(
                     filter(lambda cmd: not (any(cmd in x for x in words)), commands)