Reproduce:

• download camunda distro (7.3 or 7.2)
• log into tasklist with demo
• select review invoice task
• enter anything into the amount field
• try to complete the task

Expected:

• task gets completed, variable amount is updated

Observed:

• task does not get completed, error message: Value is not of type undefined

Reason:

• in the seeded invoice example, the amount variable is missing in the review step. Using the normal workflow, the amount variable has to be set in the start form. Then this error does not occur.