Fix key error issue

[programmerPhysicist]

Sometimes, when running the script, you will get the following error:

Traceback (most recent call last):
  File "/home/user/Workspace/habitica-workspace/Habitica-Plus-Todoist/source/oneWaySync.py", line 223, in <module>
    sync_todoist_to_habitica()
  File "/home/user/Workspace/habitica-workspace/Habitica-Plus-Todoist/source/oneWaySync.py", line 119, in sync_todoist_to_habitica
    fin_hab = main.get_hab_fromID(tid)
  File "/home/user/Workspace/habitica-workspace/Habitica-Plus-Todoist/source/main.py", line 228, in get_hab_fromID
    hab = HabTask(task['data'])
KeyError: 'data'

[programmerPhysicist]

This issue is related to a TODO in the code:
# TODO: handle error cases for response
We need to do what is said in the TODO to at least partially fix the issue. The other thing that needs to happen, is we need to stay within the rate limit of Habitica: #6