[BUGFIX] Fix overriding objects in new property mapper

It seems there is a problem with overriding objects when using the new
property mapper, using e.g.

config.tx_extbase {
 objects {
   GeorgRinger\Testoverride\Domain\Model\Fo {
    className = GeorgRinger\Testoverride\Domain\Model\Bar
   }
  }
}

Change-Id: I82c3a970bf6680dbfb5ca1ac7bc6489e15f9f9ea
Resolves: #49803
Releases: 6.2, 6.1, 6.0
[WIP] fluid widgets without sessions

Fixes: #12094
Change-Id: If11ffd7c554f1f45264a06046ecf5d50bc22690d