drop-down icon display not shown

[vishalisakar]

Describe the bug
if a custom bootstrap theme used the drop-down icon not shown. is there any way to correct it?

To Reproduce
Please, make an example there https://stackblitz.com/ to reproduce the bug and share a link to the example.

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

[optimistex]

@vishalisakar Please, make an example there https://stackblitz.com/ to reproduce the bug and share a link to the example.