SiteInfo: Don't load previews at multiselect

BUG: 451284

It looks like the signal currentItemChanged is fired before the
selectedItems is updated which makes this protection after the second
change of current selection.

This is at minimum good enough when selecting items via arrow keys.

Signed-off-by: Juraj Oravec <jurajoravec@mailo.com>

src/lib/other/siteinfo.cpp

@@ -277,7 +277,7 @@ void SiteInfo::showPixmap(QPixmap pixmap)
 
 void SiteInfo::showImagePreview(QTreeWidgetItem *item)
 {
-    if (!item) {
+    if ((!item) || (item->treeWidget()->selectedItems().length() > 1)) {
         return;
     }
     QUrl imageUrl = QUrl::fromEncoded(item->text(1).toUtf8());