Is it true that supererogatory prayers are not accepted from someone who owes make-up prayers, and they receive no reward?

The scholars have said that one who has an unfulfilled obligatory prayer should not perform supererogatory prayers, because making up missed prayers is an immediate obligation. And absolute supererogatory prayers are not valid before making up the missed obligatory prayer, due to the Prophet's (peace and blessings be upon him) saying in the Hadith Qudsi: "My servant does not draw near to Me with anything more beloved to Me than that which I have made obligatory upon him." And due to his (peace and blessings be upon him) saying regarding one who had not performed Hajj for himself: "Perform Hajj for yourself first, then perform Hajj for Shubrumah."