EllisLab/CodeIgniter — pull request #1084 by stuartgibson (2012-02-27 16:12:18+00:00)
Title: Allow NULL to be passed as value to Active Record limit() method

The current implementation in master and develop will typecast $value to an int, which means passing NULL causes limit to be set to 0. This pull request only sets ar_value if the value passed is not NULL, similar to how the same function handles offset.