!= null

index.js

@@ -647,7 +647,7 @@ function sendMessageFromMcChat(username, message) {
         if (match){
             var member = match[1].trim();
             var memberFetch = client.users.cache.find(user => user.username == member);
-            if (memberFetch){
+            if (memberFetch != null){
                 message = message.replace("@"+member, "<@" + memberFetch.id + ">");
             }
         }