fixed typo

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

@@ -434,7 +434,7 @@ this.SingleFileCore = this.SingleFileCore || (() => {
 			}
 			const content = docUtil.serialize(this.doc, this.options.compressHTML);
 			if (this.options.displayStats) {
-				const contentSize = docutil.getContentSize(content);
+				const contentSize = docUtil.getContentSize(content);
 				this.stats.set("processed", "HTML bytes", contentSize);
 				this.stats.add("discarded", "HTML bytes", size - contentSize);
 			}