getRegisteredFlexForms in AbstractItemProvider throws not catched exceptions
Affects be_group editing:
If a DS is registered that manipulates the flex form DS retrieval, resolving in getRegisteredFlexForms() may fail. Example scenario is a loaded ext:gridelements that doesn't register a default flex DS.
This code part is used to enable flex form data access right settings, and the current code needs to do a "qualified guess". It probably can only be systematically solved with either a flex form ds registry, or a convention based magic system, or a hook.
For now, we should probably just catch a possible extension at that point and ignore those cases for the flex field access right system.
Solving this case systematically would have the advantage that we might be able to do stuff like static TCA migration for flex DS, too, so in general that would be interesting to have.