make sure shadowRootsData has a length

lib/single-file/single-file-core.js

@@ -880,7 +880,7 @@ this.SingleFileCore = this.SingleFileCore || (() => {
 		async resolveShadowRootURLs() {
 			const rootOptions = this.options;
 			const batchRequest = this.batchRequest;
-			if (this.options.shadowRootsData) {
+			if (this.options.shadowRootsData && this.options.shadowRootsData.length) {
 				await resolveURLs(this.doc);
 			}