Which doesn't actually make much of a difference in this case because
this is a welded dialog, which currently does not preserve a VclPtr
owner of such dialogs.

Perhaps we should rather fix the
   SfxTabDialogController::runAsync
infrastructure to temporarily
(a) preserve an owner for such dialogs
(b) disposeAndClear such dialogs
at least until we are done with welding?

Otherwise this is very confusing.

Change-Id: I568eb6813925299663ac3f90749b64076d404d19
Reviewed-on: https://gerrit.libreoffice.org/65708
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>