#vulnerable code 
                              private void ensureTyped(NodeTraversal t, Node n, JSType type) {
    // Make sure FUNCTION nodes always get function type.
    Preconditions.checkState(!n.isFunction() ||
            type.isFunctionType() ||
            type.isUnknownType());
    JSDocInfo info = n.getJSDocInfo();
    if (info != null) {
      if (info.hasType()) {
        // TODO(johnlenz): Change this so that we only look for casts on CAST
        // nodes one the misplaced type annotation warning is on by default and
        // people have been given a chance to fix them.  As is, this is here
        // simply for legacy casts.
        JSType infoType = info.getType().evaluate(t.getScope(), typeRegistry);
        validator.expectCanCast(t, n, infoType, type);
        type = infoType;
      }

      if (info.isImplicitCast() && !inExterns) {
        String propName = n.isGetProp() ?
            n.getLastChild().getString() : "(missing)";
        compiler.report(
            t.makeError(n, ILLEGAL_IMPLICIT_CAST, propName));
      }
    }

    if (n.getJSType() == null) {
      n.setJSType(type);
    }
  } 
                            #location 13 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                              private void ensureTyped(NodeTraversal t, Node n, JSType type) {
    // Make sure FUNCTION nodes always get function type.
    Preconditions.checkState(!n.isFunction() ||
            type.isFunctionType() ||
            type.isUnknownType());
    // TODO(johnlenz): this seems like a strange place to check "@implicitCast"
    JSDocInfo info = n.getJSDocInfo();
    if (info != null) {
      if (info.isImplicitCast() && !inExterns) {
        String propName = n.isGetProp() ?
            n.getLastChild().getString() : "(missing)";
        compiler.report(
            t.makeError(n, ILLEGAL_IMPLICIT_CAST, propName));
      }
    }

    if (n.getJSType() == null) {
      n.setJSType(type);
    }
  }