Input type wrapper for generic action arguments is nullable

This breaks with the general pattern that input types are non-nullable

This is for all versions, its simply not implemented as a non-null

The issue does not name a file or test. Start by locating the input type wrapper for generic action arguments and compare its nullability with other input types across the supported versions. Done means the wrapper is non-nullable consistently and the relevant tests confirm the generated GraphQL schema.

Written by the indexing model from the issue text.