There is no RAW solution, so it's definitely up to you to decide. The real question comes down to how you view light and illusion magic. I personally would make the light be from an obvious location, giving away the character's location, but don't forget that being invisible doesn't actually change that anyway (by RAW you have to take the Hide action to remain hidden). Having the light simply existing in an area without an obvious source is perfectly acceptable as well. The real issue is being consistent with it, because a player may want to use this trick themselves later.
D&D 5E Light Emanating from an Invisible Character
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