What is Cause of NullPointerException Error When Amending Lease Asset End Date?

Summary:

When trying to amend (extend) the lease below, we are receiving the error 'java.lang.NullPointerException', as shown. We believe the error is due to trying to extend the 'Asset End Date' when that date is already in the past, as the 'Asset End Date' was the only component we are attempting to change, but the error message is cryptic and provides no indication as to the source of, nor reason for, the error. This leaves us with several questions:

1 - What is Cause of NullPointerException Error When Amending Lease Asset End Date?

2 - Is there a way to extend the 'Asset End Date' if that date has already past?