The "add a bridge" input box lost (saved)inputed bridges when click the "cancel" button

11.5.2 (based on Mozilla Firefox 91.13.0esr) (32-bit)
my system is debian stretch(linux kernel)
safer security level

The “add a bridge” input box lost (saved)inputed bridges when click the “cancel” button.
preference page:about:preferences#connection
reproduce step:
1.click “add a bridge” button to add a bridge then click “ok” button to save added bridge.
2.again click “add a bridge” button then just click “cencel” button.
3.again click “add a bridge” button you will see the input box become empty, you can’t re-edit privous added bridges configuration