let Runner#initialize empty doc and win properties

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

@@ -971,8 +971,6 @@ this.singlefile.lib.core = this.singlefile.lib.core || (() => {
 				options.insertSingleFileComment = false;
 				options.insertCanonicalLink = false;
 				options.saveFavicon = false;
-				options.doc = null;
-				options.win = null;
 				options.url = frameData.baseURI;
 				options.windowId = frameWindowId;
 				if (frameData.content) {
@@ -1063,8 +1061,6 @@ this.singlefile.lib.core = this.singlefile.lib.core || (() => {
 				options.removeAlternativeMedias = false;
 				options.removeUnusedFonts = false;
 				options.removeHiddenElements = false;
-				options.doc = null;
-				options.win = null;
 				options.url = resourceURL;
 				const attributeValue = linkElement.getAttribute(util.HTML_IMPORT_ATTRIBUTE_NAME);
 				if (attributeValue) {