Fix exception when no Accept header is set

Author: pfrazee

lib/mime.js

@@ -66,7 +66,7 @@ exports.isFileContentBinary = async function (fsInstance, filepath) {
 // for a given HTTP accept header, provide a list of file-extensions to try
 exports.acceptHeaderExtensions = function (accept) {
   var exts = []
-  accept = accept.split(',')
+  accept = (accept || '').split(',')
   if (accept.includes('text/html') || (accept.length === 1 && accept[0] === '*/*')) exts.push('.html')
   if (accept.includes('text/css')) exts.push('.css')
   if (accept.includes('image/*') || accept.includes('image/apng')) exts = exts.concat(['.png', '.jpg', '.jpeg', '.gif'])