Can this spell be dispelled by that magic item that lets you dispel a spell cast which you are a target of in Line of Sight (which gravity tells you you are in line of sight of.

What should have happened?

You're talking about Null powder ?

No, this item may be used to cancel a "eye" spell. And gravity is a "all" spell, even if the spell tells all players have LOS to it from anywhere and everywhere, it's for the purpose of "dispell" for exemple, and only theses cases.