UI does not validate HTTP hosts to exclude

Testing NEXUS-8718, Tamás Cservenák and I found that while the validation tests written pass, via the UI validation is not enforced for the invalid cases written in regards to adding "Hosts to exclude from HTTP/HTTPS proxy:" (on save or on +).
The exception seems to be for the blank/empty cases (on +) but even then no validation message appears but instead no entry is added.

Tamas and I agreed to make a distinct ticket since the NEXUS-8718 tests pass and soas not to clutter the other. This is that ticket.
This does not affect older versions of NX3 as this was newly implemented in NX3. I did not check vs NX2 however I am not sure if there is validation in NX2 considering NEXUS-8718 so there may not be anything to check anyway.
I left the priority major as the validation portion of NEXUS-8718 is untested and from a UI POV unimplemented (though again the tests pass).
This is an issue with Debug on or off. No error messages appear in the JS console or nexus log.