no selected dates in the input field with the multiselect plugin

[krava77]

Describe the bug
Hello.
I try to use the component with the multiselect plugin, but it does not put selected dates in the input field.
Could you explain how to resolve the issue?

To Reproduce
Steps to reproduce the behavior:
Here is the example on codepen for reproducing the issue.
https://codepen.io/Pavlo-Kravchuk/pen/yLQjVbg

Expected behavior
A clear and concise description of what you expected to happen.

jsfiddle.net / codepen.io / etc
https://codepen.io/Pavlo-Kravchuk/pen/yLQjVbg