Adding additional test case to Std Lib Maps

[bcchapman]

This case demonstrates the behavior of attempting to call myMap(missingKey) in that an exception is thrown. It also provides examples of how to handle this gracefully using default values via either getOrElse or for the entire map with withDefaultValue. Also included corresponding test case.

[raulraja]

LGTM! Thanks for your contribution!

[ghost]

Hi @bcchapman and thanks a lot for contributing. We've noticed that your git email is not the same you have on GitHub, hence your commits are not linked to your GitHub user. Note how in this PR the GitHub logo is shown in the commits instead of your avatar.

This is not a big problem but we can't include these commits in the list of contributions shown in the website, we don't have a way to link the contributions to your GitHub user. Again, thanks for your time!

[bcchapman]

Hi @dialelo Thanks for catching this. This was due to a different email being the default in my git client. In the future I will be sure to make sure those align.