Fix ReferenceError in DlDateTimePickerComponent._handleKeyDown

[steven-hadfield]

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
Bug fix

What is the current behavior? (You can also link to an open issue here)
On key press, a Javascript ReferenceError is triggered due to an undefined variable

What is the new behavior (if this is a feature change)?

Does this PR introduce a breaking change?
No

Please check if the PR fulfills these requirements

• [-] This PR is against the develop branch. (Please do not submit PR's to the master branch)
• The commit message follows our guidelines: https://github.com/angular/angular.js/blob/master/CONTRIBUTING.md#commit-message-format
• [-] Tests for the changes have been added (for bug fixes / features)
• [-] Docs have been added / updated (for bug fixes / features)

Other information:
Targeting master as develop is very out of date

[dalelotts]

Thanks for the PR! Sorry about making such a silly* mistake.

I'll bring develop up-to-date right now.

• Silly was not my first choice =)

[steven-hadfield]

Thanks for the quick turnaround. No worries about the mistake, we all make them