Do not return deleted icon view items after icon view deletion

This resolves Bug 1605
(cherry picked from commit d2ab408c06)

src/iconview/qiconview.cpp

@@ -2959,6 +2959,7 @@ QIconView::~QIconView()
     d->toolTip = 0;
 #endif
     delete d;
+    d = NULL;
 }
 
 /*!
@@ -3222,8 +3223,13 @@ int QIconView::index( const QIconViewItem *item ) const
 
 QIconViewItem *QIconView::firstItem() const
 {
+    if (d) {
         return d->firstItem;
     }
+    else {
+        return NULL;
+    }
+}
 
 /*!
     Returns a pointer to the last item of the icon view, or 0 if there
@@ -3234,8 +3240,13 @@ QIconViewItem *QIconView::firstItem() const
 
 QIconViewItem *QIconView::lastItem() const
 {
+    if (d) {
         return d->lastItem;
     }
+    else {
+        return NULL;
+    }
+}
 
 /*!
     Returns a pointer to the current item of the icon view, or 0 if no
@@ -3246,8 +3257,13 @@ QIconViewItem *QIconView::lastItem() const
 
 QIconViewItem *QIconView::currentItem() const
 {
+    if (d) {
         return d->currentItem;
     }
+    else {
+        return NULL;
+    }
+}
 
 /*!
     Makes \a item the new current item of the icon view.