Handle functions with no attached node in find_position_visitor.

pkg/dartino_compiler/lib/src/find_position_visitor.dart

 // Copyright (c) 2015, the Dartino project authors. Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE.md file.
 
 import 'package:compiler/src/elements/visitor.dart';
 import 'package:compiler/src/parser/partial_elements.dart';
 import 'package:compiler/src/elements/elements.dart';
 import 'package:compiler/src/tree/nodes.dart';
 
 /// Returns the innermost function in [compilationUnit] spanning [position] or
@@ skipping 49 matching lines @@
   visitFieldElement(FieldElement e, _) {
     element = findSmallestMatchingClosure(e) ?? element;
   }
 
 
   visit(Element e, [arg]) => e.accept(this, arg);
 
   visitElement(Element element, _) {}
 
   bool containsPosition(Node node) {
+    // TODO(sigurdm): Find out when [node] is null.
+    if (node == null) return false;

[danrubel, 2016/07/12 14:15:06]

Should we log something here to obtain more information?
Print a warning and info for the user to pass along to us but don't crash?

[sigurdm, 2016/08/10 09:05:11]

I prefer that we replicate it locally and fix it.

     return node.getBeginToken().charOffset <= position &&
         position < node.getEndToken().charEnd;
   }
 
   static int nodeLength(Node node) {
     return node.getEndToken().charEnd - node.getBeginToken().charOffset;
   }
 }