set default accept header

lib/single-file/single-file-util.js

@@ -199,14 +199,15 @@ function getInstance(utilOptions) {
 			return { data: options.asBinary ? "data:null;base64," : "", resourceURL };
 		}
 		try {
+			const accept = options.acceptHeaders[options.expectedType] || "*/*";
 			if (options.frameId) {
 				try {
-					response = await fetchFrameResource(resourceURL, { frameId: options.frameId, referrer: options.resourceReferrer, headers: { accept: options.acceptHeaders[options.expectedType] } });
+					response = await fetchFrameResource(resourceURL, { frameId: options.frameId, referrer: options.resourceReferrer, headers: { accept } });
 				} catch (error) {
-					response = await fetchResource(resourceURL, { headers: { accept: options.acceptHeaders[options.expectedType] } });
+					response = await fetchResource(resourceURL, { headers: { accept } });
 				}
 			} else {
-				response = await fetchResource(resourceURL, { referrer: options.resourceReferrer, headers: { accept: options.acceptHeaders[options.expectedType] } });
+				response = await fetchResource(resourceURL, { referrer: options.resourceReferrer, headers: { accept } });
 			}
 		} catch (error) {
 			return { data: options.asBinary ? "data:null;base64," : "", resourceURL };