Fix segfault when document is closed while annotation is selected

Prevent MouseAnnotation from accessing PageViewItem widgets any longer
after PageView deletes them in PageView::notifySetup().

BUGS: 378696
REVIEW: 130087

ui/pageview.cpp

@@ -956,6 +956,9 @@ void PageView::notifySetup( const QVector< Okular::Page * > & pageSet, int setup
             return;
     }
 
+    // mouseAnnotation must not access our PageViewItem widgets any longer
+    d->mouseAnnotation->reset();
+
     // delete all widgets (one for each page in pageSet)
     QVector< PageViewItem * >::const_iterator dIt = d->items.constBegin(), dEnd = d->items.constEnd();
     for ( ; dIt != dEnd; ++dIt )

ui/pageviewmouseannotation.cpp

@@ -414,6 +414,13 @@ void MouseAnnotation::cancel()
     }
 }
 
+void MouseAnnotation::reset()
+{
+    cancel();
+    m_focusedAnnotation.invalidate();
+    m_mouseOverAnnotation.invalidate();
+}
+
 /* Handle state changes for the focused annotation. */
 void MouseAnnotation::setState( MouseAnnotationState state, const AnnotationDescription & ad )
 {

ui/pageviewmouseannotation.h

@@ -93,6 +93,9 @@ public:
     /* Cancel the current selection or action, if any. */
     void cancel();
 
+    /* Reset to initial state. Cancel current action and relinquish references to PageViewItem widgets. */
+    void reset();
+
     Okular::Annotation * annotation() const;
 
     /* Return true, if MouseAnnotation demands control for a mouse click on the current cursor position. */