Hello I get the same problem with SH 1.38 on unity 2017.0.0f3, I don't know if this as been solved somewhere else.

The message is:

NullReferenceException: Object reference not set to an instance of an object
ShaderForge.SF_Node.GetInputData (System.String id)
ShaderForge.SFN_Lerp.IsUniformOutput ()
ShaderForge.SFN_If.IsUniformOutput ()
ShaderForge.SF_NodePreview.Combine ()
ShaderForge.SF_Node.RefreshValue (Int32 ia, Int32 ib)
ShaderForge.SF_Node_Arithmetic.RefreshValue ()
ShaderForge.SF_Node.OnUpdateNode (NodeUpdateType updType, Boolean cascade)
ShaderForge.SF_Node.CheckIfDirty ()
ShaderForge.SF_Editor.Update ()
System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:222)
Rethrow as TargetInvocationException: Exception has been thrown by the target of an invocation.
System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:232)
System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MethodBase.cs:115)
UnityEditor.HostView.Invoke (System.String methodName, System.Object obj) (at C:/buildslave/unity/build/Editor/Mono/HostView.cs:272)
UnityEditor.HostView.Invoke (System.String methodName) (at C:/buildslave/unity/build/Editor/Mono/HostView.cs:265)
UnityEditor.HostView.SendUpdate () (at C:/buildslave/unity/build/Editor/Mono/HostView.cs:341)
UnityEditor.EditorApplication.Internal_CallUpdateFunctions () (at C:/buildslave/unity/build/Editor/Mono/EditorApplication.cs:109)

if I try to open it on Unity 5.6.1f1 i d'ont don't get the sema thing, I get:

ArgumentException: The requested value 'glcore' was not found.
System.Enum.Parse (System.Type enumType, System.String value, Boolean ignoreCase) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System/Enum.cs:692)
System.Enum.Parse (System.Type enumType, System.String value) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System/Enum.cs:547)
ShaderForge.SF_Parser.ParseRenderer (System.String[] arr, Boolean only)
ShaderForge.SF_Parser.ExtractShaderForgeData (UnityEngine.Shader s, System.Single& version, Boolean setPath, Boolean findRenderers, Boolean findLOD)
ShaderForge.SF_Parser.ParseNodeDataFromShader (ShaderForge.SF_Editor editor, UnityEngine.Shader s)
ShaderForge.SF_Editor.InitializeInstance (UnityEngine.Shader initShader)
ShaderForge.SF_Editor.Init (UnityEngine.Shader initShader)
ShaderForgeMaterialInspector.OnInspectorGUI () (at Assets/ShaderForge/Editor/InternalResources/Inspectors/ShaderForgeMaterialInspector.cs:85)
UnityEditor.InspectorWindow.DrawEditor (UnityEditor.Editor editor, Int32 editorIndex, Boolean rebuildOptimizedGUIBlock, System.Boolean& showImportedObjectBarNext, UnityEngine.Rect& importedObjectBarRect) (at C:/buildslave/unity/build/Editor/Mono/Inspector/InspectorWindow.cs:1229)
UnityEditor.DockArea:OnGUI()

I put the shader code if this can be usefull.

https://drive.google.com/file/d/1S2-zvuD_YzuOi_xp5QLnJayPmQacs7VQ/view?usp=sharing