BUG: Fixed error in passing position of key press

Thanks to Maarten Beek for pointing this out on the VTK users list.

Change-Id: Ic964ff5bb3b8c69560ff7c80a1a0eee976ff5be3
Merge topic 'context-interactor-key-bug' into master

9a918305 BUG: Fixed error in passing position of key press