ngx-bootstrap Loss of modal backdrop when opening second modal

Bug description:

When opening a second modal immediately after closing the first one, the modal backdrop disappears after a short flickering when the second modal is opened. This issue has been observed since version 10.0.0 and is independent of the Angular version. The problem was introduced by a change made with a pull pequest in October 2022 (#6518). I could narrow it down to the line change in "bs-modal.service.ts": See the commit

Here is a StackBlitz that reproduces the issue: https://stackblitz.com/edit/clkau7?file=src%2Fapp%2Fapp.component.ts

Versions of ngx-bootstrap, Angular, and Bootstrap:

ngx-bootstrap: 10.0.0 (and onwards)

Angular: not relevent

Bootstrap: not relevent

Expected behavior:

The modal backdrop should remain stable and visible even when opening a second modal immediately after closing the first one.

Additional Information:

There is another open issue which was caused by the same PR: #6608

Thank you for your attention and support in addressing this issue.