Fixes the undefined offset notice when no project is assigned to a task

Steps to reproduce:
1. Create an task in any workspace in Asana.
2. Do not associate this task to any project.
3. Open asana time tracker
4. Select the workspace under which you created the task.

Expected result : User should be notified "NO PROJECT" under the project.

Actual result : Gets an error : 
Notice: Undefined offset: 0 in /var/www/apps/asana/AsanaApi.php on line 66

This PR would fix this.