Description of problem:
On the global advance settings  after i update the value of :image_inspector_cve_url: , 
I can't set back the value to empty one.
I get the message "Configuration changes saved" but the value remain as it was before.
looks like general problem, i can't remove value from other settings as well.

Version-Release number of selected component (if applicable):
5.9.0.4

How reproducible:
Always

Steps to Reproduce:
1. go to EVM--> Configuration --> Advance TAB
2. try to remove one of the settings that have value --> Save
3. 

Actual results:
The value will remain

Expected results:
The value will remove (be empty value)

Additional info: