Patch 2 for arrays that contain only one elements

For arrays that contain only one element, `(array_keys($tmp) == range(0, count($tmp) - 1)` always returns true.

`(array_keys($tmp) === range(0, count($tmp) - 1)` works as expected.

My local test environment = Linux Mint + PHP 5.4.

This patch is identical to https://github.com/XaminProject/handlebars.php/pull/66, but applies to a different part of the code.