Flagging issue is broken when we change the values of field options

Problem

Flagging an issue does not work in JIRA Agile if Custom Field configuration is modified

Steps to reproduce

• Edit 'Flagged' field and change the Field Searcher to 'None'
• Re-index

Actual Results

• Flagging issues does not work

Expected Results

• Flagging works as normal

Original description

From a user : "I tested the flagging feature and it worked nicely "out of the box". I then customized the list of option values for the custom 'Flagged' field (changed wording on "Impediments" to "Impeded" and added "Priority") and re-indexed. Now, I can add a flag in Plan mode through right-click but issues no longer display with the flag icon or the yellow color, and right-click options no longer display the "Remove Flag" option, only the "Add Flag option (although the flag has already been added)."

(see https://confluence.atlassian.com/display/GH/GreenHopper+6.2.3+Release+Notes?focusedCommentId=373260654#comment-373260654)