Is it obligatory to fulfill a vow to wear the niqab that was vowed in a dream after being saved from the problem that was the reason for the vow?

The sleeper is not held accountable until he awakens. Thus, he is not taken to task for what he utters during his sleep. So, if he makes a vow, his vow is not valid and he is not obligated to fulfill it. For the Messenger of Allah, peace and blessings be upon him, said: "The pen has been lifted from three: from the sleeper until he awakens, from the insane person until he regains his sanity, and from the child until he reaches puberty." As for the ruling on a woman wearing the niqab, it is obligatory.