Removed element.scope() calls by using the scope which we compile with

Makes ngDialog work with AngularJS 1.3 when $compileProvider debug info is disabled ($compileProvider.debugInfoEnabled(false)).
@petercrona there's no need in undefined as well just `var scope;` is enough :)

btw if you're willing to setup variable to `undefined` explicitly it's better to call `void 0` instead.