C2021-018 logic to support showing Alarm Point RO info in the step Editor

PROMS/Volian.Controls.Library/RTBItem.cs

@@ -869,6 +869,7 @@ namespace Volian.Controls.Library
 			}
 			else
 			{
+				if (MyStepPanel == null) return; // C2021-018 check for null reference (display alarm point table info in editor)
 				if (MyStepRTB.Focused) // If active Set BackColor to the active color
 					MyStepRTB.BackColor = MyStepPanel.ActiveColor;
 				else // Otherwise Set the BackColor to either the InactiveColor or the AnnotationColor