What do you mean by "while attempting to upgrade". Does it happen when you run the migration from 4.3.4 to 5 or at some other time?
BTW: It is a good practice to migrate from the newest release of one version to the newest release of the other (i.e. from 4.3.7 to 5.0.2 rather than from 4.3.4 to 5.0) since the newe releases often have bugfixes for migration-issues.