Debugger: Do not warn SOFT_ASSERT when no debugger is selected

Do not not try to update the debugger if none is actually set. This
avoids triggering a SOFT_ASSERT in the debuggeritemmodel.

Change-Id: I646e251f58d6e25f1a88bddc142d953f94522084
Reviewed-by: hjk <hjk121@nokiamail.com>
Debugger: Do not lose the engine type in the debuggeritemmodel

Have the DebuggerItemConfigWidget remember the engine type (even
though it does not display it), so that it can write that information
back into the model later.

Change-Id: I1ed0d6a8d3750696a7eb5c453179acc282b78ce4
Reviewed-by: hjk <hjk121@nokiamail.com>