Fix: nested styles refer to top-level parent in sourcemap line number

In the meantime I did find that if I added
outputStyle: 'compressed' to the sass-task it now works for Chrome, but not FF.

gulp.task( 'sass', function() {
   return gulp.src( paths.sass.main.generate )
              .pipe( load.plumber( { errorHandler: reportError } ) )
              .pipe( load.sourcemaps.init( { largeFile: true } ) )
              .pipe( load.sassGlob() )
              .pipe( load.sass( { outputStyle: 'compressed' } ) )
              .pipe( load.postcss( processors.modules ) )
              .pipe( load.lineEndingCorrector() )
              .pipe( load.sourcemaps.write( 'assets/scss/' ) )
              .pipe( gulp.dest( paths.root.main ) );
} );