catch promise rejection

bot.js

@@ -675,7 +675,10 @@ client.on('message', message => {
                 break;
 
             case 'async':
-                asyncImageRequest(message);
+                asyncImageRequest(message)
+                    .catch(error => {
+                        sendToBotTestingChannel(error.message);
+                    });
                 break;
 
             // Voice commands