ModelBinderAttribute should not throw from BinderType property setter

[pranavkm]

https://github.com/aspnet/Mvc/blob/dev/src/Microsoft.AspNet.Mvc.ModelBinding/BinderMetadata/ModelBinderAttribute.cs#L34-L57

The BinderType setter throws when the type is not an IModelBinder. This is problematic since reflecting over the type decorated with the attribute would produce an exception. We already throw from the code consuming the attribute, which should suffice.

Example:

[ModelBinder(BinderType = typeof(string)]
public class MyModel {}

typeof(MyModel).GetCustomAttributes() <-- will throw

[rynowak]

Example callstack? ModelMetadata? The code you provided is not common.

[ianhong]

9daf6b4