Fix string.split returning an empty table if string starts with sepearator (#7827)

Fix string.split returning an empty table if string starts with sepearator (#7827)

Calling string.split(":A:B:C:D", ":") returns an empty array.
This is due to first empty string not making repeat loop decreasing max_split which has a 0 value when reaching until.
Changing max_splits default value from -1 to -2 fixes that issue.