fix(log): no longer emitting 'undefined' for $log.info/err/etc in IE

[colincasey]

Closes #1705

[mary-poppins]

Thanks for the PR!

• Contributor signed CLA now or in the past
  • If you just signed, leave a comment here with your real name
• PR's commit messages follow the commit message format

If you need to make changes to your pull request, you can update the commit with git commit --amend.
Then, update the pull request with git push -f.

Thanks again for your help!

[colincasey]

Just signed the CLA a short while ago. My real name is Colin Casey as you may have guessed from my screen name :)

[btford]

Landed as 4ff1a65.