wallpapers/image: reset grid index after new images are added

Otherwise the index will still be the old index.

BUG: 455129
FIXED-IN: 5.26
(cherry picked from commit fe9604ca)

wallpapers/image/imagepackage/contents/ui/ThumbnailsComponent.qml

@@ -36,6 +36,7 @@ Item {
         function onWallpaperBrowseCompleted() {
             // Scroll to top to view added images
             wallpapersGrid.view.positionViewAtIndex(0, GridView.Beginning);
+            wallpapersGrid.resetCurrentIndex(); // BUG 455129
         }
     }