I’m not sure what I did to get this error
NullReferenceException: Object reference not set to an instance of an object
UnityEditor.Graphs.Edge.WakeUp ()
(at C:/buildslave/unity/build/Editor/Graphs/UnityEditor.Graphs/Edge.cs:114)
UnityEditor.Graphs.Graph.DoWakeUpEdges (System.Collections.Generic.List1[T] inEdges, System.Collections.Generic.List
1[T] ok, System.Collections.Generic.List`1[T] error, System.Boolean inEdgesUsedToBeValid) (at C:/buildslave/unity/build/Editor/Graphs/UnityEditor.Graphs/Graph.cs:387)
Restarting unity worked.