fixed malformed data URI issue

lib/single-file/single-file-browser.js

@@ -40,7 +40,10 @@ this.SingleFile = this.SingleFile || (() => {
 			} catch (error) {
 				return options && options.asDataURI ? "data:base64," : "";
 			}
-			const contentType = resourceContent.headers.get("content-type");
+			let contentType = resourceContent.headers.get("content-type");
+			if (contentType) {
+				contentType = contentType.match(/^([^;]*)/)[0];
+			}
 			if (options && options.asDataURI) {
 				try {
 					const buffer = await resourceContent.arrayBuffer();