[Formatting] Checked token for null, before using the parent.

ICSharpCode.NRefactory.CSharp/Formatter/AstFormattingVisitor.cs

@@ -874,10 +874,12 @@ namespace ICSharpCode.NRefactory.CSharp
 				}
 				ForceSpacesBeforeRemoveNewLines(rParToken, spaceWithinMethodCallParentheses);
 			}
+			if (!rParToken.IsNull) {
 				foreach (CSharpTokenNode comma in rParToken.Parent.Children.Where(n => n.Role == Roles.Comma)) {
 					ForceSpacesBefore(comma, spaceBeforeMethodCallParameterComma);
 				}
 			}
+		}
 
 		public override void VisitMethodDeclaration(MethodDeclaration methodDeclaration)
 		{
@@ -1777,10 +1779,12 @@ namespace ICSharpCode.NRefactory.CSharp
 				}
 				ForceSpacesBeforeRemoveNewLines(rParToken, spaceWithinMethodCallParentheses);
 			}
+			if (!rParToken.IsNull) {
 				foreach (CSharpTokenNode comma in rParToken.Parent.Children.Where(n => n.Role == Roles.Comma)) {
 					ForceSpacesBefore(comma, spaceBeforeMethodCallParameterComma);
 				}
 			}
+		}
 
 		public override void VisitInvocationExpression(InvocationExpression invocationExpression)
 		{