`bug`: `activeDomains` tracked incorrectly if multiple tabs with same domain exist

[sannidhyaroy]

Issue:

If multiple tabs with the same configured domain exist, on removal of one such tab, the associated domain is removed from the activeDomains array, even though other tabs are still mapped to the same domain.

Expected behavior:

Domain must be removed from activeDomains, only when no other tabs are mapped to it.