Fix qrc icon

Apparently the icon was not null, because the mimetype was known.
But there was no icon associated with it and we got an
icon which is not null, but has a null pixmap.

src/kitemviews/kstandarditemlistwidget.cpp

@@ -1488,7 +1488,8 @@ QPixmap KStandardItemListWidget::pixmapForIcon(const QString& name, const QStrin
         if (icon.isNull()) {
             icon = QIcon(name);
         }
-        if (icon.isNull()) {
+        if (icon.isNull()
+            || icon.pixmap(size / qApp->devicePixelRatio(), size / qApp->devicePixelRatio(), mode).isNull()) {
             icon = fallbackIcon;
         }