member() to check for namedMembers length

[4vanger]

Run into a problem having an import like

import 'nprogress/nprogress.css';

and sorting rule like

            sort: member(unicode),

Import object will look like:

{
  start: 340,
  end: 372,
  importStart: 340,
  importEnd: 372,
  type: 'import',
  moduleName: 'nprogress/nprogress.css',
  namedMembers: []
}

and sorting will throw. Solution: add check for array length, let it return undefined and sort based on that