Partial events deserialize but don't return data.

[pakrym]

EventGridEvent.Parse(@"{""data"":""""}").Single().GetData<string>();

Would fail with the argument null exception during GetData call

Related to: #15058
cc @ellismg

[ellismg]

FWIW, @JoshLove-msft, In JavaScript land, we throw an error in our parser if the data is malformed (i.e. there are JSON errors) or any required fields of the event type are missing (or are of the wrong type)).