gracefully handle null subscription on trusted onSubscribe the same as non-trusted already does
add try/catch in example to better demonstrate error handling

… despite no errors being possible of being thrown in this code
more thorough error handling in case Func1 implementation itself fails

- Func1.call may fail (null impl, bad impl, etc)
- Func1.call may success but the implementation itself may throw an exception instead of properly catching and sending to onError
Merge pull request #189 from benjchristensen/polishing

Handful of Improvements