Maybe I've misunderstood the use of the "Fix for Version(s)" field, but I understand it to be where you identify in which version of the code a particular issue will be addressed.

i.e. the Affected Version(s) field would record in what version(s) the issue was found, then when a solution had been found, then the version(s) that provided that solution would be recorded in the "Fix for Version" field.

If this is the case maybe "Fixed in Version(s)" would seem a more appropriate label perhaps.