Replace AddIdentical

What it fixes

The original just has a typo in the for loop.

The code

replace AddIdentical(obj, i)
{
    local j

    for (j=1; j<=i.#plural_of; j++)
    {
        if i.plural_of #j = 0           ! a blank slot
        {
            i.plural_of #j = obj    ! add it
            return j
        }
    }
    return false
}