`walk` should not use `splice` when removing an array element

[ghost]

walk should use the delete operator when removing elements from arrays, instead of Array#splice.

Expected:

JSON.parse("[1, 2, 3]", function (key, value) {
  if (typeof value == "object" && value) {
    return value;
  }
}).length == 3;

Actual:

JSON.parse("[1, 2, 3]", function (key, value) {
  if (typeof value == "object" && value) {
    return value;
  }
}).length == 0;