Copied style is null. Using StyleNotFound instead.

[willlogs]

this is weird! I'm using unity 2018.3.5f1
I'm getting these in console:

Copied style is null. Using StyleNotFound instead.
UnityEngine.GUIStyle:.ctor(GUIStyle)
SubjectNerd.PsdImporter.PsdImportWindow:LoadStyles() (at Assets/PsdToUnity/Editor/PsdImportWindow.cs:170)
SubjectNerd.PsdImporter.PsdImportWindow:OnGUI() (at Assets/PsdToUnity/Editor/PsdImportWindow.cs:352)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

NullReferenceException: Object reference not set to an instance of an object
SubjectNerd.PsdImporter.PsdImportWindow.LoadStyles () (at Assets/PsdToUnity/Editor/PsdImportWindow.cs:174)
SubjectNerd.PsdImporter.PsdImportWindow.OnGUI () (at Assets/PsdToUnity/Editor/PsdImportWindow.cs:352)
System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at :0)
Rethrow as TargetInvocationException: Exception has been thrown by the target of an invocation.
System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at :0)
System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) (at :0)
UnityEditor.HostView.Invoke (System.String methodName, System.Object obj) (at C:/buildslave/unity/build/Editor/Mono/HostView.cs:342)
UnityEditor.HostView.Invoke (System.String methodName) (at C:/buildslave/unity/build/Editor/Mono/HostView.cs:336)
UnityEditor.HostView.InvokeOnGUI (UnityEngine.Rect onGUIPosition, UnityEngine.Rect viewRect) (at C:/buildslave/unity/build/Editor/Mono/HostView.cs:310)
UnityEditor.DockArea.DrawView (UnityEngine.Rect viewRect, UnityEngine.Rect dockAreaRect, System.Boolean customBorder, System.Boolean floatingWindow, System.Boolean isBottomTab) (at C:/buildslave/unity/build/Editor/Mono/GUI/DockArea.cs:361)
UnityEditor.DockArea.OldOnGUI () (at C:/buildslave/unity/build/Editor/Mono/GUI/DockArea.cs:320)
UnityEngine.Experimental.UIElements.IMGUIContainer.DoOnGUI (UnityEngine.Event evt, UnityEngine.Matrix4x4 worldTransform, UnityEngine.Rect clippingRect, System.Boolean isComputingLayout) (at C:/buildslave/unity/build/Modules/UIElements/IMGUIContainer.cs:244)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

[Apoll0]

Same problem
Unity 2019.2.2f1

[Apoll0]

Try change PsdImportWindow.cs, row 220
tempStyle = GUI.skin.FindStyle("VisibilityToggle");
to
tempStyle = GUI.skin.FindStyle("Toggle");

[paternostrox]

Same problem on 2019.2.8f1
@Apoll0 solution worked for me.