MultiSelect page - console error: Duplicates in a repeater are not allowed

[Semalexa]

open http://formstamp.github.io/#/multiselect
type in 'Where have you been?' field any value from its list
the error will be added to console

Error: [ngRepeat:dupes] Duplicates in a repeater are not allowed. Use 'track by' expression to specify unique keys. Repeater: item in items, Duplicate key: string:Algeria, Duplicate value: "Algeria" http://errors.angularjs.org/1.3.2/ngRepeat/dupes?p0=item%20in%20items&p1=string%3AAlgeria&p2=%22Algeria%22 minErr/<@http://formstamp.github.io/app.js:4458:13 ngRepeatAction@http://formstamp.github.io/app.js:28545:22 $watchCollectionAction@http://formstamp.github.io/app.js:18287:14 $RootScopeProvider/this.$get</Scope.prototype.$digest@http://formstamp.github.io/app.js:18420:24 $RootScopeProvider/this.$get</Scope.prototype.$apply@http://formstamp.github.io/app.js:18682:14 NgModelController</this.$$debounceViewValueCommit@http://formstamp.github.io/app.js:25020:8 NgModelController</this.$setViewValue@http://formstamp.github.io/app.js:24992:8 baseInputType/listener@http://formstamp.github.io/app.js:23785:8 createEventHandler/eventHandler@http://formstamp.github.io/app.js:7357:10

return logFn.apply(console, args);