When opening this dialog, the tab items are decorated with images
created by the individual search panels. When the dialog is closed,
those images are disposed again.

Problem arises because the search panels don't create new images, but
instead use shared images. Meaning when the dialog is opened a second
time, those images have already been disposed, preventing the dialog
from showing up.

Reason for this regression is the switch from the Icons class of the
bndtools project to the PDE Resources class. Former has an explicit
"isDisposed()" check, which would've created a new image on-the-fly,
while latter doesn't. Given that the images are not owned by this
dialog, the solution to this problem is to simply not have them be
disposed by the dialog.

See https://github.com/eclipse-pde/eclipse.pde/issues/1365