[INTERNAL] fix for commit 1bb89e178b202294520d545f12326ac4c3d956c9

Shame on me, I should not try to access widgets outside of the SWT
thread.

Change-Id: I856beef0a86e3067354be028babfe71949425880
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1728
Tested-by: Jenkins-Eclipse QA
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>