chocolateboy 605adc922d allow PluginPass.file.addImport to create empty import statements (#6022)
* allow PluginPass.file.addImport to create empty import statements; fixes #6021

omitting addImport's second argument creates an import statement with an
empty `specifiers` array i.e. an empty import statement:

plugin:

    Program (path, { file }) {
        file.addImport('foo-bar/register')
    }

output:

    import "foo-bar/register";
2017-07-28 12:37:00 -04:00
..
2015-11-11 12:07:23 -08:00