1.4.0 alpha 4 NullReferenceException on Physics.Raycast

i just upgraded to 1.4.0 alpha 4 from 1.3.0 and a graph that was working fine in 1.3.0 is now giving me a NullReferenceException. this pic is from play mode:

here is the error message in the console:

NullReferenceException: Object reference not set to an instance of an object
Bolt.Flow.GetConvertedValue (Bolt.ValueInput input)
Bolt.InvokeMember.Invoke (Bolt.Flow flow)
Bolt.InvokeMember.Enter (Bolt.Flow flow)
Bolt.Flow.InvokeDelegate (Bolt.ControlInput input)

i had to connect the control input and output of the Physics.Raycast for 1.4.0 alpha 4, even though i didn't have it connected in 1.3.0. and i tried replacing various units, and restarting Unity, to no avail.

not sure if this is a bug – would appreciate any help. thanks!

Unity 2017.4.3f1 on MacOS 10.13.5

EDIT: in play mode the droplet animations suggest that the layer mask is not sending anything up to the Physics.Raycast, while everything else is.

EDIT: and, when i substitute the Physics.Raycast that doesn't have a LayerMask input, i don't get any error on the raycast, so to me it looks like the LayerMask literal is not working properly.

actually, correction. 

this works:

but this doesn't:

so i guess it could be the hit info?

if i use the raycast that doesn't give a hitinfo, it works. so i guess it is a hitinfo problem.