Regression introduced by commit 8d4eb292b2
in 6.0, when QTaggedPointer was introduced. We set the tag even when the
loading failed and failed to reset it because d = {} retains the tag.
Pick-to: 6.2 6.4
Fixes: QTBUG-103387
Change-Id: Ie4bb662dcb274440ab8bfffd170a07aa9c9ecfca
Reviewed-by: Marc Mutz <marc.mutz@qt.io>