Entity Attributes Filter: Invalid script produces 400, subsequent saves produce original error message

Tested in 1.5.0-SNAPSHOT-6c05a36 on http://shibboleth-ui.unicon.net/dashboard

Description

Steps
Log into UI https://shibboleth-ui.unicon.net/
Click 'Add New' button and select 'Metadata Provider’
Choose a provider type that supports Entity Attributes filters (such as FileBackedHttpMetadataResolver)
Create a basic provider
Finish/Save the provider
From the dashboard, on the provider just created, click 'Manage Filters'
Click 'Add Filter'
For filter type, choose 'EntityAttributes'
Enter a 'Name'
For 'Search By', choose 'Script'
Enter any bogus script
Attempt to save
Note the 400 error
Enter a valid script (something as simple as: true;)
Attempt to save
Note the same 400 error containing the old script
Click Cancel
Note that there are now two Entity Attributes Filters
Edit each one, checking the script

What is occurring
Failed/bogus scripts produce a 400 but save anyway. Once this occurs, fixing the script and saving results in a duplicate Filter being created.

What is expected
No filter should be created until a script is successfully handled and a save completes properly.