When an element is associated with another diagram and the "Don't show this
dialog in the future (unless the SHIFT key is pressed)" checkbox is checked on
the "Element Navigation" dialog for a selected diagram to open, the "Element
Navigation" dialog should not come up and associated diagram should open but
it's not opened.

Repro steps:
- create a uml project
- create 2 activity diagrams
- create and name a couple of invocation elements on each diagram
- from one of the element on the 1st diagram, right click and select "Associate
With..." from the context menu
- from the "Associate" dialog, enter a string that matches the 2nd diagram name
and click on Find
- from the result, select the 2nd diagram fromthe Search Result table
- check the "Automatically Set the Navigate on Double-Click Option" checkbox
- click on "Associate" button
- close the dialog. a lock is displayed on the upper-right corner of the element
on the diagram
- from the 1st diagram, double click on the element with the lock
- the "Element Navigation" dialog, select the associated diagram row on the table
- check the checkbox for "Don't show this dialog in the future (unless the SHIFT
key is pressed)" and click on OK. the associated diagram opens. double clicking
on the element should automatically opens the associated diagram or bring the
associated diagram to the front if already opened but the "Element Navigation"
dialog opens instead.