Api task streak default value (#13557)

* Default value for task streak (fix #13372)

* Truncate task streak value decimals on update

website/server/controllers/api-v3/tasks.js

@@ -688,6 +688,8 @@ api.updateTask = {
           -user.preferences.timezoneOffset,
         ).date()];
       }
+      if (task.streak === undefined) task.streak = 0;
+      task.streak = Math.trunc(task.streak);
     }
 
     setNextDue(task, user);