New definition of "empty" for the GetTasksEvent

[guilhermednt]

GetTasksEvent now considers the Stack empty if there is only an IntentTask in it.

This is done to avoid the following:

1. Non-authenticated user tries to access resource X
2. X is Stacked as an IntentTask
3. User logs in
4. addTaskIfStackEmpty will not add needed tasks
5. IntentTask is consumed, but now addTaskIfStackEmpty will add the needed task that was not added before
6. User enters a Task an doesn't even see resource X

Fixes PROCERGS#679