**Do you want to request a _feature_ or report a _bug_?**

Report a bug.

**What is the current behavior?**

When testing components, `Warning: ReactComponentTreeDevtool: Missing React element for debugID 1 when building stack` is shown when calling `TestUtils.renderIntoDocument`.

**If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem via https://jsfiddle.net or similar (template: https://jsfiddle.net/reactjs/69z2wepo/).**

https://github.com/angusfretwell/reproduce-debugid-warning (`npm install && npm test`).

**What is the expected behavior?**

According to #7187 this is an internal warning and shouldn't be displayed.

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**
- react@15.2.1
- react-addons-test-utils@15.2.1
- react-dom@15.2.1

I didn't receive this warning on 15.2.0.

* @param {?object} nestedChildNodes Nested child maps.
   * @return {?object} A set of child instances.
   * @internal
   */
  instantiateChildren: function(
    nestedChildNodes,
    transaction,
    context,
    selfDebugID 
  ) {
    if (nestedChildNodes == null) {
      return null;
    }
    var childInstances = {};
    if (__DEV__) {
      traverseAllChildren(
        nestedChildNodes,
        (childInsts, child, name) => instantiateChild(
          childInsts,
          child,
          name,
          selfDebugID
        ),
        childInstances
      );
    } else {
      traverseAllChildren(nestedChildNodes, instantiateChild, childInstances);
    }
    return childInstances;
  },