Assets/UI: Sanity check argument for UILayout.template_asset_view()

Was already doing some sanity checks, but wasn't checking if the passed
property actually is a collection property, which is important.

source/blender/editors/interface/interface_template_asset_view.cc

@@ -162,6 +162,10 @@ static void asset_view_template_refresh_asset_collection(
     RNA_warning("Asset collection not found");
     return;
   }
+  if (RNA_property_type(assets_prop) != PROP_COLLECTION) {
+    RNA_warning("Expected a collection property");
+    return;
+  }
   if (!RNA_struct_is_a(RNA_property_pointer_type(&assets_dataptr, assets_prop),
                        &RNA_AssetHandle)) {
     RNA_warning("Expected a collection property for AssetHandle items");