I was creating a custom GUI in a blank game template, which I have two inventory windows shown always visable. I tried to name one of the inventory windows, which I accidently named the same as a label which I got an error message saying I can't name it that. I clicked again to change the name and this error popped up.
Error: Object reference not set to an instance of an object.
Version: AGS 3.1.1.67
System.NullReferenceException: Object reference not set to an instance of an object.
at AGS.Editor.GUIEditor.bgPanel_MouseMove(Object sender, MouseEventArgs e)
at System.Windows.Forms.Control.OnMouseMove(MouseEventArgs e)
at System.Windows.Forms.Control.WmMouseMove(Message& m)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
Thanks for reporting this, I'll look into it.
Let me know if it happens again.