"If there is a surviving spouse and no personal representative has been appointed, the surviving spouse may file a joint return for the year of death."

In some cases the worst thing for the surviving spouse to do is file a joint return, especially in cases like this where there is a balance due.  Make sure your malpractice insurance is paid before assisting with such a mistake.  But if a surviving spouse comes to you after someone else helped file a joint return, remember that the personal representative has a year to correct the error.