Update patch with blank `remove` section removes selected nodes?

[machship-mm (Mike McKay)]

Non-nullable field was not present in result from Dgraph

This does seem counter-intuitive. The correct way to delete a node should be to use the deleteType mutation. A node shouldn’t be deleted if the user supplies an empty remove object. We should ignore the mutation in this case. This has also been reported by another user Update patch with blank `remove` section removes selected nodes? and I think we should change the behavior to have no effect.

@JatinDevDG I agree that this must be treated as a bug; it is completely counterintuitive to delete something based on a wildcard update clause.