3.VIS 4

报错信息为：
System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
---> System.NullReferenceException: Object reference not set to an instance of an object.
at Pinta.Core.DocumentLayers.SetCurrentUserLayer(Int32 i) in D:\项目代码\Pinta1.2_InOverlay\Source\Pinta\Pinta.Core\Classes\DocumentLayers.cs:line 683
at Pinta.Core.DocumentLayers.SetCurrentUserLayer(UserLayer layer) in D:\项目代码\Pinta1.2_InOverlay\Source\Pinta\Pinta.Core\Classes\DocumentLayers.cs:line 734
at Pinta.Gui.Widgets.LayersListWidget.HandleLayerSelected(Object o, EventArgs e) in D:\项目代码\Pinta1.2_InOverlay\Source\Pinta\Pinta.Gui.Widgets\Widgets\Layers\LayersListWidget.cs:line 166
--- End of inner exception stack trace ---
at System.RuntimeMethodHandle.InvokeMethod(Object target, Span`1& arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
at System.Delegate.DynamicInvokeImpl(Object[] args)
at GLib.Signal.ClosureInvokedCB(Object o, ClosureInvokedArgs args)
at GLib.SignalClosure.MarshalCallback(IntPtr raw_closure, IntPtr return_val, UInt32 n_param_vals, IntPtr param_values, IntPtr invocation_hint, IntPtr marshal_data)