Context:

In the following scenario, users are able to create an empty variable filter which leads to the report evaluation failing ("Error loading report"):

1. Create a report for a definition that has both a correlating and a bool variable. (eg Analysis Testing Process)
2. Open the variable filter modal and select correlating variable
3. Select a random value 
4. Change the variable selection to boolVar
5. Do not select any value but just clilck "Add Filter"
6. An empty boolvar filter has been created and the report can no longer be evaluated

Note: I've only been able to recreate this with switching from correlating variable to boolvar.

AT:

• Users cannot save a variable filter without a selected value