sorry for your loss. many joint filers have had issues e-filing their return when one spouse has died in 2019. are you sure the IRS is asking for salary because to e-file, the norm is the prior year AGI for 2018 (1040 line 7). on a joint return for 2019 where a joint return was filed for 2018 the AGI for both of you would be the same. form 1310is required.
if nothing works you'll have to mail in the return. for your husband sign your name and as surviving spouse.
