Error message does not display in Error pop-up modal

**Severity**: low

**Description**: Error message for exception in event handler for kernel_dead.Session is undefined.


Start by locating the error pop-up modal and the event handler for kernel_dead.Session in the website sources, then reproduce the exception shown in the issue. Done means the exception's error message is displayed in the modal instead of appearing undefined.

索引モデルが issue の本文から書いたものです。