I don't have a solution, but I want to report that I've experienced the same crash. I've submitted multiple crash/diagnostic reports to Apple in the last month or so.
I concur that the problem is related to Safari's storage of Passwords. If I have Passwords Autofill enabled, Safari will prompt me to save/update passwords for websites. Instead of properly prompting, Safari crashes with a SIGABRT signal. Autofill still works, however, if I enter a password on a new website or change a password, Safari will recognize this and crash when it ostensibly attempts to prompt me to save it. For that reason, I've been leaving Autofill disabled most of the time.
I would much prefer to use Autofill, but this bug makes it effectively useless in Safari since I can no longer add/update without Safari crashing.
Safari Version 26.1 (19622.2.11.119.1) on MacOS 14.8.2