fix($ionNavView): prevent read property 'name' of null

Closes #1587

Author: alexpods

js/angular/directive/navView.js

@@ -129,7 +129,7 @@ function( $ionicViewService,   $state,   $compile,   $controller,   $animate) {
         // to derive our own qualified view name, then hang our own details
         // off the DOM so child directives can find it.
         var parent = element.parent().inheritedData('$uiView');
-        if (name.indexOf('@') < 0) name  = name + '@' + (parent ? parent.state.name : '');
+        if (name.indexOf('@') < 0) name  = name + '@' + ((parent && parent.state) ? parent.state.name : '');
         var view = { name: name, state: null };
         element.data('$uiView', view);