QmlDesigner: Clear content library search field on model attach

This makes it in line with search fields of other view.

Fixes: QDS-9237
Change-Id: Idfb703600582fd5b06e4120d7e7d1e233f2781fd
Reviewed-by: Mahmoud Badri <mahmoud.badri@qt.io>

src/plugins/qmldesigner/components/contentlibrary/contentlibraryview.cpp

@@ -132,6 +132,8 @@ void ContentLibraryView::modelAttached(Model *model)
     m_widget->setHasQuick3DImport(m_hasQuick3DImport);
 
     m_sceneId = model->active3DSceneId();
+
+    m_widget->clearSearchFilter();
 }
 
 void ContentLibraryView::modelAboutToBeDetached(Model *model)