Error not thrown on failure to extend

[sandwichsudo]

I'm not sure whether this is a problem with grunt-sass, node-sass or even libsass, but I'm finding with an otherwise empty .scss file, compiling eg

.foo{
    @extend .bar;
}

does not throw an error saying something "The selector ".bar" was not found.", when it should.

[drewwells]

Sassmeister link: http://sassmeister.com/gist/560bc02d4a53355640fc

Looks to be reproducing on master as well.

[xzyfer]

This is a known issue #871