No warning shown for slow filter

Steps to reproduce

1. Open Advanced tab in options page
2. Add custom filter /foo/

Observed behavior

Filter added to list but no warning shown next to it

Expected behavior

Filter added to list and warning shown next to it

Further information

The slow property is correctly assigned and the filter is then added to the customFilters array but since the component doesn't use that array - except during initialization - it ignores that object and relies on the object it creates itself.