How can I resolve Civi Dashboard Javascript error: widget.name is null?
I'm glad you found the cause of your problem. It does sound like something went wrong back when you originally created those dashlets, and it's not clear what that was. But it would be good to proactively repair this during the upgrade.

I've created a PR to do so: https://github.com/civicrm/civicrm-core/pull/9672