Implemented safeget method for email retrieval for some clients

Hi Constantin,

I recently came across a problem - the code was throwing an exception when my requests did not ask for the email address of a user, only a basic profile (I did not care about it and did not want to ask more than I needed). 

I went and changed the code to use SafeGet method to just save null if the response does not contain email.

P.S. This project is awesome and saved me a ton of time

Thank you

Roman Tumaykin