KB-1013 "There was an error in an expression in null at null: null" error thrown attempting to publish a process model

Symptoms

When users attempt to publish a process model, they are shown the following validation error:

There was an error in an expression in null at null: null

No error is produced in the logs.

Cause

The process model is referencing a deleted object within an expression. The most common root cause is a swim lane pointing to a deleted process variable, deleted constant, or deleted group.

Action

Map the process model object to an existing item (e.g. fix the assignment lane).

Affected Versions

This article applies to Appian 7.8 and later.