Debugger: Remove breakpoint mark from assembler view

... after deletion. The breakpoint itself was actually removed from
the breakpoint view but the red blob stayed until the next update
(e.g. after the next 'step')

Change-Id: I120059a6e643df7c104a8f6d96e09b9c707d14d8
Reviewed-by: Niels Weber <niels.weber@theqtcompany.com>

src/plugins/debugger/breakhandler.cpp

@@ -1331,6 +1331,8 @@ BreakpointItem::~BreakpointItem()
 
 void BreakpointItem::destroyMarker()
 {
+    if (m_engine)
+        m_engine->updateBreakpointMarkers();
     if (m_marker) {
         BreakpointMarker *m = m_marker;
         m->m_bp = 0;