If a newer version of MediaWiki gets rolled back, it's possible for
there to be lint entries in the database that don't exist according to
CategoryManager.
Instead of showing an error to the user, just silently hide those rows.
All callers to CategoryManager::getCategoryId() already check the
category exists. The callers for CategoryManager::getCategoryName() will
catch the MissingCategoryException, and log it if necessary. Notably
LinterError::makeLintError() will return false on invalid rows, and all
callers have been updated to handle that.
Bug: T179423
Change-Id: Ia5f56f18a51fa871511b02410222a6079efbfff6
