### **Environment**:

Your OpenProject Version: 12.0.1

### **Steps to reproduce:**

1. Create a work package custom field, tick 'Used as a filter'

2. Create a work package query using this custom field as a filter

3. Edit the custom field and uncheck 'Used as a filter'

4. Open the work package query and try to export as, say, XLS


Also broken in this scenario:

* The filter button shows e.g. (2) filters in the count badge, but only one is shown in the filter configuration list, so users cannot remove it

* "Save" and "Save as" don't work, errors are thrown in the console, but no error message appears on screen


### **Actual Behavior**

A red error message with "Bad request."

### **Expected Behavior**

The export should Begin of the insertionwork.End of the insertion Begin of the deletion let the user know this is due to the no longer available field in filter query.End of the deletion
The Begin of the insertioninvalidEnd of the insertion filter field is Begin of the insertionomitted (not shown inEnd of the insertion Begin of the deletion displayed with a red warning string andEnd of the deletion the Begin of the insertioncount badge orEnd of the insertion Begin of the deletion option forEnd of the deletion the Begin of the insertionfilter list).End of the insertion Begin of the deletion user to remove it from their filtersEnd of the deletion
Begin of the insertionSaving or saving as does work without throwing an exception inEnd of the insertion Begin of the deletion On saving/"saving as"End of the deletion the Begin of the insertionconsoleEnd of the insertion Begin of the deletion query, the invalid filter field is removed (instead of crashing angular)End of the deletion

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