Call to a member function getField() on null in ee/ExpressionEngine/Addons/fluid_field/ft.fluid_field.php:158 when using Preview

Seeing above error when using the Preview functionality.

Enabling all error output leads to this notice

Undefined offset: 844 ee/ExpressionEngine/Addons/fluid_field/ft.fluid_field.php, line 158

Thought this is due to some Fluid field that had been deleted, so I tried to filter out the ID (field ID 844). After doing so same error with different ID came up. Looking at the existing Fluid field IDs I noticed that the IDs that cause the undefined offset seem to be bogus IDs, since our Fluid field IDs end at something like 200.

As a quick fix I added this line to the ft.fluid_field.php at line 157 - obviously no real fix, but it works for now.

if($id>400): continue; endif;

EE version is 7.2.12 with no additional plugins/add-ons.

Any idea what’s causing the original error?

Thanks: Lars Schwarz