fixed parsing of imported templates

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

@@ -942,6 +942,7 @@ this.singlefile.lib.core = this.singlefile.lib.core || (() => {
 				options.insertFaviconLink = false;
 				options.doc = null;
 				options.win = null;
+				options.content = null;
 				options.url = resourceURL;
 				if (!Util.testIgnoredPath(resourceURL) && Util.testValidPath(resourceURL)) {
 					const processor = new Runner(options);