NPE import develop

Fix possible NPE in import dialog
see http://trac.openmicroscopy.org.uk/ome/ticket/11953

Test 1
 * Log in as user 12 (no project)
 * Click on Import
 * Select an image, click arrow to add to the queue.
 * Switch group. 
 * Do not import

Test 2
 * Log in as user-11 (no project)
 * Repeat the steps above.

--rebased-from #2046