Fix crash on closing

Tell the document we're no longer an observer in the destructor
BUGS: 346149
FIXED-IN: KDE Applications 15.04.1

ui/magnifierview.cpp

@@ -35,6 +35,12 @@ MagnifierView::MagnifierView(Okular::Document* document, QWidget* parent)
   , m_document(document)
   , m_page(0)
 {
+  document->addObserver(this);
+}
+
+MagnifierView::~MagnifierView()
+{
+  m_document->removeObserver(this);
 }
 
 void MagnifierView::notifySetup(const QVector< Okular::Page* >& pages, int setupFlags)

ui/magnifierview.h

@@ -30,6 +30,7 @@ class MagnifierView : public QWidget, public Okular::DocumentObserver
 
   public:
     MagnifierView( Okular::Document *document, QWidget *parent = 0 );
+    ~MagnifierView();
 
     void notifySetup( const QVector< Okular::Page * > & pages, int setupFlags );
     void notifyPageChanged( int page, int flags );

ui/pageview.cpp

@@ -396,7 +396,6 @@ PageView::PageView( QWidget *parent, Okular::Document *document )
     d->magnifierView = new MagnifierView(document, this);
     d->magnifierView->hide();
     d->magnifierView->setGeometry(0, 0, 351, 201); // TODO: more dynamic?
-    document->addObserver(d->magnifierView);
 
     connect(document, SIGNAL(processMovieAction(const Okular::MovieAction*)), this, SLOT(slotProcessMovieAction(const Okular::MovieAction*)));
     connect(document, SIGNAL(processRenditionAction(const Okular::RenditionAction*)), this, SLOT(slotProcessRenditionAction(const Okular::RenditionAction*)));