Deriveds where under certain conditions not detected as dirty correctly. The reason is that a transitive check_dirtiness call could update the flag of a derived, even if the condition doesn't ulimately result to true. That's why the check for "is now dirty" needs to be moved out of the inner if block.
Fixes#11481
This may also fix a yet undetected overfiring bug in the "is unowned" case because the previous inner "is now dirty?" check didn't take unowned into account.
Simon H