Bug 436322 - [Model] IAE when back button is clicked after closing all
perspectives

Change-Id: I33119998849d04fc84cfebed9c0cbd1fba3cbaed
Bug 169947 - [EditorMgmt] Should not show dialog when closing workbench
window with dirty editor opened in another window

Change-Id: I2dc06d7995ea4fd3e580a103cb5fc9e3e6c179b4