I get this error when trying to access my Apps -> Websites -> [Website] settings on my DW 9.2.6 installation.
https://www.screencast.com/t/PffSScHbIw
I think it is related to data in one of my custom fields.
It is a "Link" field where a add reference to a page with ID 84. But it looks like DW is adding an extra ',' that mess up the conversion you are doing behind the scenes.
Have no idea on how the extra ',' ends up here, but I have not done anything special to provoke it.