изменено по использование встроенного делегата

WarmlyLocomotive/WarmlyLocomotive/FormLocomotiveCollection.cs

@@ -44,6 +44,10 @@ public partial class FormLocomotiveCollection : Form
     /// <param name="e"></param>
     private void ButtonAddLocomotive_Click(object sender, EventArgs e)
     {
+        if(_company == null)
+        {
+            return;
+        }
         FormLocomotiveConfig form = new();
         // TODO передать метод
         form.AddEvent(SetLocomotive);

WarmlyLocomotive/WarmlyLocomotive/FormLocomotiveConfig.cs

@@ -16,7 +16,7 @@ public partial class FormLocomotiveConfig : Form
     /// <summary>
     /// Событие для передачи объекта
     /// </summary>
-    private event LocomotiveDelegate? LocomotiveDelegate;
+    private event Action<DrawningLocomotive>? LocomotiveDelegate;
 
     /// <summary>
     /// Конструктор
@@ -34,15 +34,13 @@ public partial class FormLocomotiveConfig : Form
         panelBlue.MouseDown += Panel_MouseDown;
 
         buttonCancel.Click += (events, e) => Close();
-
-
     }
 
     /// <summary>
     /// Привязка внешнего метода к событию
     /// </summary>
     /// <param name="locomotiveDelegate"></param>
-    public void AddEvent(LocomotiveDelegate locomotiveDelegate)
+    public void AddEvent(Action<DrawningLocomotive> locomotiveDelegate)
     {
         LocomotiveDelegate += locomotiveDelegate;
     }