TypeError: array_keys(): Argument #1 ($array) must be of type array, null given in array_keys() (line 280 of core/modules/views/src/Plugin/views/filter/InOperator.php).

Can we get a real issue summary here? When is this happening? What other modules are you using? Can you reproduce this on a clean Drupal install?

Just adding an isset() is usually just masking the real issue.

I have restored the standard issue template. Moving to 11.x, this needs to be fixed there first and then considered for backport.

Thanks for updating the issue summary, that helps. There are still questions from a maintainer that should be answered, "When is this happening? What other modules are you using? Can you reproduce this on a clean Drupal install?"

And I see that an exposed filter is used. There are many issues related to exposed filters, has a search of those issues been done to ensure this is not a duplicate? This search link → may help with that.