validation cannot be removed from attached observable

[crissdev]

The validatable extender provides a way to remove any validation defined on the observable by using it like observable.extend({validatable: false}). This fails when using the minified version of Knockout because the extender attempts to access internal fields from Knockout library which are not exported.

var obsv = ko.observable().extend({validatable: true});
obsv.isModified.subscribe(function() { });

// The line fails
obsv.extend({validatable: false});