Fix #4172 donation validation display error

[jimmyli97]

Resolves #4172

Description

• donation items are now correctly displayed after invalid edit would bring inventory to below distributed amount
• rspec request test for above

Alternatives considered

• in the rspec, not sure how specific to be in the error message test, I added tests for both using Events and not using Events
• in the rspec, not sure if it's better to use factorybot create(:distribution) instead of PUT

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• manual testing
• bundle exec rake

Screenshots