Group By: Select all filtered result not checked when previously search and select all filtered items

[userTtt123]

Step to reproduce:

1. Open Group By select
2. Type "euro" and click Select all filtered result https://cuppalabs.github.io/angular2-multiselect-dropdown/#/groupby
3. Open select one more time, type the same "euro". All item is checked, but Select all filtered result checkbox is unchecked

This issue reproduce just for grouped select. How I can fix it?