Merge remote-tracking branch 'origin/4.12'

Change-Id: Ib95ec2c50c4bbaefd4ed0ec5af191ccc846c824f

src/plugins/debugger/debuggerengine.cpp

@@ -386,6 +386,10 @@ public:
         // This triggers activity in the EngineManager which
         // recognizes the rampdown by the m_perpective == nullptr above.
         perspective->destroy();
+
+        // disconnect the follow font size connection
+        TextEditorSettings::instance()->disconnect(this);
+
         delete perspective;
     }