[MultiComboBox] n-more label not working in read-only mode

[hristop]

When the MultiComboBox is in read-only mode and has few selected items, which cause it to show the n-more label, there is no way to see those selected items, as the n-more does not react when pressed.

1. Go to the MultiComboBox test page
2. If needed shrink the screen so the n-more label is shown.
3. Try clicking on the read-only MultiComboBox's n-more label