I cannot create a subject

I get this error when i try to create a topic. What is the cause?

Hi @RawShed and welcome :slight_smile: A
Are you using a custom preview template? If so can you share the template code, the way you’re registering it and your config.yml?
Looks like you’re passing a null value in your custom code.
Sharing the repo will also be of great help if you can.

@erez Github repo: https://github.com/fuatcangenc/gatsby-deneme

Hi @RawShed, it looks like the image can be null here:

Some posts don’t have the cover property.