- fixed problem in C# MmsValue

dotnet/IEC61850forCSharp/MmsValue.cs

@@ -336,6 +336,10 @@ namespace IEC61850
 				if ((type == MmsType.MMS_ARRAY) || (type == MmsType.MMS_STRUCTURE)) {
 					if ((index >= 0) && (index < Size ())) {
 						IntPtr value = MmsValue_getElement (valueReference, index);
+
+						if (value == IntPtr.Zero)
+							return null;
+						else 
 							return new MmsValue (value);
 					} else
 						throw new MmsValueException ("Index out of bounds");