Prevent votingResult query for absinthe global createDelegation

[jinjagit]

Currently, we permit votingResult query from a successful createDelegation mutation, even for a global delegation (needs confirmation).

This is nonsensical, since a delegate could have voted on more than one specific proposal (or proposal + voting_method combo).

[jinjagit]

Closing, as correctly returns null for proposalUrl, votingResult or votingMethod query of global delegation. #227 ensured the null for votingMethod in this case.