Fix checking wrong property in `TryGetVariableType()`

[amylizzle]

I guess I only tested the case where the tag and variable name happened to match. Whoops.

BackingField.Name is the var name ie BackgroundColor Attribute.Tag is the DataField tag name ie background-color

[PJB3005]

Does this work if the data field name is inferred automatically? i.e.

[DataField]
public int Foobar { get; set; }

[amylizzle]

It does! For some reason it automatically applied camelCase in my test, but the inferred name worked as a query.