Debugger: Handle failed breakpoints as unclaimed

Change-Id: I02a44db5391b174e75fc326ce217b271ee73c464
Reviewed-by: Denis Shienkov <denis.shienkov@gmail.com>
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/debugger/breakhandler.h

@@ -93,6 +93,7 @@ private:
     friend class BreakHandler;
     friend class BreakpointManager;
     friend class BreakpointMarker;
+    friend class DebuggerEngine;
 
     void updateMarker();
     void updateMarkerIcon();