Pre-condition: International Dialing rule should be enabled (Unmanaged Gateway ' U-7' should be added to International dialing rule)

Steps:
1)Navigate to System-->Dial plans page
2)Go to International dialing rule page
3)Select the added gateway (U-7) checkbox and click on Remove button
4)gives an error "Add at least one gateway before enabling the rule."
At this stage, the operation appears to have completed succesfully - The gateway is removed and the dial plan gets disabled.
5)Click on OK button which intern navigates to Dial Plans main page
6)Now again navigate to International dialing rule page to check whether the gateway has been removed?

Expected result:
The Gateway has been removed from the dial plan

Actual Result:
Gateway U-7 has not been removed from the International dialing rule

Attached file:
snapshot