Cecil's ExceptionHandler.HandlerEnd can be null

* Impl/ExecutionPathFactory.cs: Do not throw an ArgumentNullException if
'end' is null since Cecil's ExceptionHandler.HandlerEnd can be null when
the method's last instruction is part of the handler. Uncommon IL that
can be generated by CSC

gendarme/rules/Gendarme.Rules.Exceptions/Impl/ExecutionPathFactory.cs

@@ -17,8 +17,6 @@ public IList<ExecutionPathCollection> CreatePaths (Instruction start, Instructio
 		{
 			if (start == null)
 				throw new ArgumentNullException ("start");
-			if (end == null)
-				throw new ArgumentNullException ("end");
 
 			List<ExecutionPathCollection> paths = new List<ExecutionPathCollection> ();
 			CreatePathHelper (start, end, new ExecutionPathCollection (), paths);