wallpapers/image: add current image to list if it's not in list

The current wallpaper image can be set by a Plasma script. In that case,
the wallpaper is not added to the list, so also check the current image
is already added after opening the config dialog.

BUG: 458364
FIXED-IN: 5.26

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

@@ -24,9 +24,13 @@ Item {
     Connections {
         target: imageWallpaper
         function onLoadingChanged() {
-            if (!imageWallpaper.loading) {
-                wallpapersGrid.resetCurrentIndex();
+            if (imageWallpaper.loading) {
+                return;
             }
+            if (configDialog.currentWallpaper === "org.kde.image" && imageModel.indexOf(cfg_Image) < 0) {
+                imageWallpaper.addUsersWallpaper(cfg_Image);
+            }
+            wallpapersGrid.resetCurrentIndex();
         }
 
         function onWallpaperBrowseCompleted() {

wallpapers/image/plugin/imagebackend.cpp

@@ -376,7 +376,7 @@ void ImageBackend::slotWallpaperBrowseCompleted()
 
 QString ImageBackend::addUsersWallpaper(const QUrl &url)
 {
-    auto results = static_cast<ImageProxyModel *>(wallpaperModel())->addBackground(url.toLocalFile());
+    auto results = static_cast<ImageProxyModel *>(wallpaperModel())->addBackground(url.isLocalFile() ? url.toLocalFile() : url.toString());
 
     if (!m_usedInConfig) {
         m_model->commitAddition();