Some empty selector sets pass the previous guard clause

[spicycode]

For example, we were seeing a selector of "" that didn't get caught, and subsequently raised an exception on down the line.

[spicycode]

cc: @leongersing

[josh]

Could you add a failing test? These lines should function the same.

[spicycode]

@josh We couldn't get anything to work re: running it locally (boxen says everything is kosher, but it didn't work). This change was a result of chasing down a failure inside of gist, and we've been unable to recreate it outside of gist.

[josh]

Maybe you aren't running the latest version. That line was only added 4 days ago 54dab87.

[spicycode]

That was the line in question that we had to patch, see https://github.com/josh/selector-set/pull/5/files#diff-5d3757768563b0c40226d91384aedcdfR308

[spicycode]

I'm trying to create a test to recreate the failure, as well as retrying the update that exposed the issue in the app.

[josh]

The only way this change could make a difference is if this.selectors is anything other than an Array. In that case, it would be a symptom of a different bug.