fix custom emoji

lib/rocketchat/utils.js

@@ -96,6 +96,9 @@ utils.processFileAttachment = async function (context, message, attachment) {
 }
 
 utils.srcPath = function (srcDir, filename) {
+  if (!srcDir || !fs.existsSync(srcDir)) {
+    return false
+  }
   const files = fs.readdirSync(srcDir).filter((fn) => fn.startsWith(filename));
   if (files.length !== 1) {
     return false
@@ -151,6 +154,23 @@ utils.copyFile = function (src, dest) {
   }
 }
 
+utils.downloadGridFSByName = async function (context, collection, filename, dest) {
+  if (!fs.existsSync(path.dirname(dest))) {
+    fs.mkdirSync(path.dirname(dest), { recursive: true })
+  }
+  if (fs.existsSync(dest)) {
+    fs.unlinkSync(dest)
+  }
+
+  const bucket = context.rocketchat.gridFsBucket(collection.collectionName)
+  const destStream = fs.createWriteStream(dest)
+  bucket.openDownloadStreamByName(filename).pipe(destStream)
+  return new Promise((resolve, reject) => {
+    destStream.on('finish', resolve)
+    destStream.on('error', reject)
+  })
+}
+
 utils.downloadGridFS = async function (context, collection, id, dest) {
   if (!fs.existsSync(path.dirname(dest))) {
     fs.mkdirSync(path.dirname(dest), { recursive: true })