When String#split is used with an empty string as the field seperator it effectively splits the original string into chars, and there is a pre-existing fast path for this using SPLIT_TYPE_CHARS. However this path creates an empty array in the smallest size pool and grows from there, despite already knowing the size of the desired array. This commit pre-allocates the correct size array in this case in order to allow the arrays to be embedded and avoid being allocated in the transient heap