Custom field option removed, affected issues not picked up by 'is EMPTY' condition though shown as having no value

I've created a Custom Field named 'Inv Field 1' as Select List. I've added options white, blue, red to the custom field. Then I created a number of issues, some assigned blue, some red, and some none. Now that I removed option blue from the Custom Field, the 'blue' issues lost their value as on the first screen. But it appeared it has not become the same as none because 'is EMPTY' didn't pick up them. (Look at the second screen.)