Train stop Add Filter in Lines Manager cannot be undone without removing stop

Issue description

If you click "Add Filter", you get the filter boxes. But there is no way to undo this without deleting the stop. I would expect the Add Filter button to toggle this panel. It's particularly harmful since adding an empty/default filter has unintended consequences (the train no longer does anything at the station).

Reproduction steps

Reproducible on any train stop in any line.

Game version and build number

0.73 b436

Operating system

Windows

This was fixed in one of our previous updates. Thanks for reporting it!