Describe the bug
self.message_buffer is a Queue object. In Python, a Queue instance
is always truthy regardless of whether it's empty, so the check
if self.message_buffer: never evaluates to False.

To Reproduce

• Run any config that uses the TwitterInput plugin
• The buffer check on line ~13777 of twitter.py always passes
• get_nowait() is called even on an empty queue, relying on the
  Empty exception as control flow rather than an intentional guard

Expected behavior
The code should check if not self.message_buffer.empty(): to
properly guard the get_nowait() call.

System Information (please complete the following information):

• Operating System: [Windows 10]
• Python Version: [e.g. v3.11]