Notice error in Ajax quiz on direct url quiz take

Problem/Motivation
The Ajax quiz notice errors when directly access the question numbers on Ajax quiz enabled.

Replication Steps
1. Create normal quiz(make sure more than 2 questions in quiz) with ajax quiz enabled
2. Take the quiz
3. After complete first question via ajax or skipped by ajax. Try to access question by URL.
Example:
Quiz node id is 16.
Access question as http://example.com/node/16/take/2
4. After this accessing, any question will give notice error.

Proposed resolution
Need to check and confirm array key exist.

Remaining tasks
Nil

User interface changes
Nil

API changes
Nil

Data model changes
Nil

Thanks advance,
Arunkumar K