resetPointer = () => {
    // Create tree is called to normalize the stack into VTree and allow
    // middleware to hook into the parser.
    const newTree = createTree(stack.pop());

    // Reset the pointer to the parent.
    pointer = stack[stack.length - 1];
    pointer.childNodes.push(newTree);
  }
Allow short-circuiting if never found.
@type {number|null}