Filter box gets blocked after deleting filter expression with keyboard

[ohrenkino]

Could you follow the rules for bug reports:

@Florian

While posting a bug report

• Provide step-by-step instructions on how to reproduce bug.
• Report only one bug per topic. Open multiple topics for multiple bugs.
• Choose a topic title that explains the problem.

So far I don't see a step-by-step description and I doubt that the filter box is really "blocked" and cannot be activated again, so probably, the topic does not explain the problem.