XF 1.5 Mysqli statement execute error

[Zaino60]

Dear Xenforo Community,
I recently found an error in my log which wasn't letting users to reply in a certain thread. You can see the error here: http://pastebin.com/4DDcn9Vb
More info: https://gyazo.com/89d90cb9f31ad8371b3361702092eb04
What is this error about? Is it harmful for my forums or I just ignore it? How can I fix it?
- My Xenforo Version is 1.5.0
- I'm not using a custom template or style
- This error still happens with modifications/plugins disabled
Thanks!

 

[Mike]

Does this happen every time you try to reply? That would seem to indicate something unexpected is happening as we check if you're already watching the thread before trying to do this insert.

 

[Zaino60]

Does this happen every time you try to reply? That would seem to indicate something unexpected is happening as we check if you're already watching the thread before trying to do this insert.

It only happened once apparently, but I wanted to know if I can ignore it because it was a one-time thing or if I should do something with the configurations or the MySQL database

 

[Mike]

If it only happened once, it should be safe to ignore.