Fix compile issue when there is no quick3dassetimport module

Change-Id: I769a977f8422e002ed5680c1788aa6d3948f0534
Reviewed-by: Mahmoud Badri <mahmoud.badri@qt.io>

src/plugins/qmldesigner/components/itemlibrary/itemlibraryassetimporter.cpp

@@ -491,6 +491,7 @@ bool ItemLibraryAssetImporter::generateComponentIcon(int size, const QString &ic
 
 void ItemLibraryAssetImporter::finalizeQuick3DImport()
 {
+#ifdef IMPORT_QUICK3D_ASSETS
     if (!isCancelled()) {
         // Don't allow cancel anymore as existing asset overwrites are not trivially recoverable.
         // Also, on Windows at least you can't delete a subdirectory of a watched directory,
@@ -532,6 +533,7 @@ void ItemLibraryAssetImporter::finalizeQuick3DImport()
             notifyFinished();
         }
     }
+#endif
 }
 
 bool ItemLibraryAssetImporter::isCancelled() const