Bug: 400 when attempting to save an Entity Attributes Filter with an entity id that doesn't match the group's regex

Steps to reproduce:

1. Create a provider that supports filters
2. Create an Entity Attributes filter with the following payload (note the entity id):

   {"@type":"EntityAttributes","filterEnabled":false,"entityAttributesFilterTarget":{"entityAttributesFilterTargetType":"ENTITY","value":["oihawef"]},"relyingPartyOverrides":{"signAssertion":false,"turnOffEncryption":false,"forceAuthn":false,"dontSignResponse":false,"ignoreAuthenticationMethod":false,"useSha":false,"omitNotBefore":false},"name":"1"}

3. Save

Expected result: The filter should save
Actual result: A 400 is returned with no response body, resulting in a blank pink rectangular toast message in the UI

Note that saving with an entity id that does match the group's regex works fine.