fix coverity issues

src/Gui/GuiApplication.cpp

@@ -73,6 +73,7 @@ bool GUIApplication::notify (QObject * receiver, QEvent * event)
     if (!receiver) {
         Base::Console().Log("GUIApplication::notify: Unexpected null receiver, event type: %d\n",
             (int)event->type());
+        return false;
     }
     try {
         if (event->type() == Spaceball::ButtonEvent::ButtonEventType || 

src/Gui/Selection.cpp

@@ -38,7 +38,6 @@
 #include "Document.h"
 #include "Selection.h"
 #include "SelectionFilter.h"
-#include "SelectionObjectPy.h"
 #include "View3DInventor.h"
 #include <Base/Exception.h>
 #include <Base/Console.h>
@@ -47,6 +46,7 @@
 #include <App/Document.h>
 #include <App/DocumentObject.h>
 #include <App/DocumentObjectPy.h>
+#include <Gui/SelectionObjectPy.h>
 #include "MainWindow.h"
 
 
@@ -981,6 +981,7 @@ SelectionSingleton::SelectionSingleton()
     hz = 0;
     ActiveGate = 0;
     App::GetApplication().signalDeletedObject.connect(boost::bind(&Gui::SelectionSingleton::slotDeletedObject, this, _1));
+    CurrentPreselection.Type = SelectionChanges::ClrSelection;
     CurrentPreselection.pDocName = 0;
     CurrentPreselection.pObjectName = 0;
     CurrentPreselection.pSubName = 0;

src/Gui/View3DInventorViewer.cpp

@@ -841,9 +841,10 @@ void View3DInventorViewer::setNavigationType(Base::Type t)
     }
 
     NavigationStyle* ns = static_cast<NavigationStyle*>(base);
-    ns->operator = (*this->navigation);
-    if (this->navigation)
+    if (this->navigation) {
         ns->operator = (*this->navigation);
+        delete this->navigation;
+    }
     this->navigation = ns;
     this->navigation->setViewer(this);
 }