Hello, recently we upgraded from xenforo 1.5 and now it seems I'm met with a conversation alert for a message that has no content and is dated Dec 31 1969

Here's what it looks like when I click the icon:

When I click the conversation message I'm met with the following error.

Does anyone know where I can start?

Here's what it looks like when I click the icon:

When I click the conversation message I'm met with the following error.

Does anyone know where I can start?