use func_get_args to pass array_prepend call through to Arr::prepend …

[trnxpace]

Currently calling array_prepend() with a missing third ($key) argument calls Arr::prepend() with three arguments, the third being the default null value from the array_prepend() definition. However, Arr::prepend() uses func_num_args() to check if the third argument is set. This leads to the element being prepended with an empty key (and any subsequent calls of array_prepend() (without supplying a third argument) overwriting the inserted element).

Using ...func_get_args() leads to the third argument of the Arr::prepend() call not being set if no third argument is supplied to array_prepend(), thus enabling correct handling of numeric indices.