Ensure that a port can only unregister its frameId if it's associated
Ensure that a port can only unregister its frameId if it's associated

This is a more complete fix for issue #2125.

poacher2k/vimium,poacher2k/vimium,smblott-github/vimium,decaffeinate-examples/vimium,decaffeinate-examples/vimium,gdh1995/vimium,philc/vimium,philc/vimium,decaffeinate-examples/vimium,smblott-github/vimium,gdh1995/vimium,gdh1995/vimium,philc/vimium,smblott-github/vimium,poacher2k/vimium