The wither and bloom spell reads, in part (Strixhaven: A Curriculum of Chaos, p. 38):
[...] one creature of your choice in that area can spend and roll one of its unspent Hit Dice and regain a number of hit points equal to the roll plus your spellcasting ability modifier.
Does this mean the healing from the wither and bloom spell can only happen if the creature has at least one unspent Hit Die?
Or does the spell still heal a number of hit points equal to the spellcasting modifier, even if the creature has no unspent Hit Dice?