Fixing JS error on dataRequested event

The js assumes that targetId isn't null, but it is if there is no
attribute.

Pull Request: master
oops meant to commit this
Merge branch 'master' into target-id-bug

Conflicts:
	ZeroClipboard.min.js
updating targetel check
Merge pull request #83 from jonrohan/target-id-bug

Fixing JS error on dataRequested event