testing #64214:

• in a task use an input variable with an unknown name ${input:unknown}
• run the task

Observe:

• the variable is not substituted and there is no error popping up.

Since a task with an unresolved variable makes no sense (and might be even dangerous if the ${...} is passed to a real shell) I suggest to popup an error alert (not a notification) indicating a need for immediate attention.