properties and the outline views are stacked

Regression from bug 485154: If the properties view is hidden do not
react on activation of parts in the same stack.

Fix: If the Properties view is hidden do not react on activation of a
part if the contributing part is in the same stack as the Properties
view.

Change-Id: I0ff0e6b51d5bf26c2d6a90738d3173332df713c1
Signed-off-by: Rolf Theunissen <rolf.theunissen@altran.com>
Signed-off-by: Andrey Loskutov <loskutov@gmx.de>