refactor: Use plural wording for user tweets trigger

packages/backend/src/apps/twitter/info.json

@@ -233,8 +233,8 @@
       ]
     },
     {
-      "name": "User Tweet",
+      "name": "User Tweets",
-      "key": "userTweet",
+      "key": "userTweets",
       "description": "Will be triggered when a specific user tweet something new.",
       "substeps": [
         {

packages/backend/src/apps/twitter/triggers.ts

@@ -1,15 +1,15 @@
 import TwitterClient from './client';
-import UserTweet from './triggers/user-tweet';
+import UserTweets from './triggers/user-tweets';
 import SearchTweets from './triggers/search-tweets';
 
 export default class Triggers {
   client: TwitterClient;
-  userTweet: UserTweet;
+  userTweets: UserTweets;
   searchTweets: SearchTweets;
 
   constructor(client: TwitterClient) {
     this.client = client;
-    this.userTweet = new UserTweet(client);
+    this.userTweets = new UserTweets(client);
     this.searchTweets = new SearchTweets(client);
   }
 }

packages/backend/src/apps/twitter/triggers/user-tweets.ts

@@ -1,6 +1,6 @@
 import TwitterClient from '../client';
 
-export default class UserTweet {
+export default class UserTweets {
   client: TwitterClient;
 
   constructor(client: TwitterClient) {

packages/backend/src/models/flow.ts

@@ -55,7 +55,7 @@ class Flow extends Base {
       .orderBy('created_at', 'desc')
       .first();
 
-    return (lastExecution as Execution).internalId;
+    return lastExecution ? (lastExecution as Execution).internalId : null;
   }
 
   async $beforeUpdate(