Why am I getting this compile error?

I have come across this compile error whilst designing a car game using EasyRoads3D:

ArgumentException: The thing you want to instantiate is null. UnityEngine.Object.CheckNullArgument (System.Object arg, System.String message) (at C:/BuildAgent/work/d3d49558e4d408f4/artifacts/EditorGenerated/UnityEngineObject.cs:104) UnityEngine.Object.Instantiate (UnityEngine.Object original) (at C:/BuildAgent/work/d3d49558e4d408f4/artifacts/EditorGenerated/UnityEngineObject.cs:90) NewEasyRoads3D.OnGUI () (at Assets/EasyRoads3D/Editor/NewEasyRoads3D.cs:97) System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/monoAndRuntimeClassLibs/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/monoAndRuntimeClassLibs/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:232) System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) (at /Users/builduser/buildslave/monoAndRuntimeClassLibs/build/mcs/class/corlib/System.Reflection/MethodBase.cs:115) UnityEditor.HostView.Invoke (System.String methodName, System.Object obj) (at C:/BuildAgent/work/d3d49558e4d408f4/Editor/Mono/GUI/DockArea.cs:231) UnityEditor.HostView.Invoke (System.String methodName) (at C:/BuildAgent/work/d3d49558e4d408f4/Editor/Mono/GUI/DockArea.cs:224) UnityEditor.HostView.OnGUI () (at C:/BuildAgent/work/d3d49558e4d408f4/Editor/Mono/GUI/DockArea.cs:120)

I would really appreciate any help with this, if anyone needs any more details please get back to me