QmlDesigner: Fix textures becoming misaligned in a search

When doing a search, some textures appeared misaligned. This was caused
by the fact that the "invisible" (i.e. hidden) textures had their Image
set correctly as invisible but the delegate itself remained visible.

Task-number: QDS-9234
Change-Id: Ia2cd6f4f6795bb435567b8915e770b78461babed
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>
Reviewed-by: Miikka Heikkinen <miikka.heikkinen@qt.io>

share/qtcreator/qmldesigner/contentLibraryQmlSource/ContentLibraryTexture.qml

@@ -23,6 +23,8 @@ Item {
     property alias progressValue: progressBar.value
     property alias progressText: progressLabel.text
 
+    visible: root.delegateVisible
+
     signal showContextMenu()
 
     function statusText()