Multiple tag issue

[pixeldepth]

I found problem with multiple tag. There is no possibility to type some tag more than once.

You can see it in the last example "Tagging without dropdown" on https://ng-select.github.io/ng-select#/tags

Reproduce problem:

1. Type some tag name (for example "abc") and accept it by pressing enter
2. Remove tag
3. Type one more time the same tag ("abc") and press enter. This time tag can't be added.

After that you can only add different tag, but also only once.