Misleading error message 2069

[SomMeri]

Fixes #2069 - raise an error in case of an empty extend selector.

Note: I'm not sure why values order in source map changed. It does not seem to be caused by my change, it was failing before I made them.

[SomMeri]

Travis is failing this with this message:

>> PhantomJS has crashed. Please read the crash reporting guide at https://github.com/ariya/phantomjs/wiki/Crash-Reporting and file a bug report at https://github.com/ariya/phantomjs/issues/new with the crash dump file attached: /tmp/0d8033aa-5104-667c-04c1b3db-2ea3fc33.dmp 0 [ 'PhantomJS has crashed. Please read the crash reporting guide at https://github.com/ariya/phantomjs/wiki/Crash-Reporting and file a bug report at https://github.com/ariya/phantomjs/issues/new with the crash dump file attached: /tmp/0d8033aa-5104-667c-04c1b3db-2ea3fc33.dmp' ]

Did someone encountered it before? I'm not sure how I can solve it. I guess it helps nobody, but it really works on my machine.

[seven-phases-max]

I'm not sure why values order in source map changed

It depends on the installed source-map module version. v0.1.34 (I had installed before today) produces the old order, while current v0.1.37 produces new one. So I guess it's OK (we need to just update our node modules).

[SomMeri]

I merged in upstream changes and tests passed now.

[lukeapage]

ah thanks @seven-phases-max, on the ball as usual.