universe_create_locations.php: don't unset $sector
universe_create_locations.php: don't unset $sector

The `$sector` variable is a special global, and should not be
overwritten (i.e. dont' use it as the temporary object of a for-loop).

This also fixes a PHP warning that `$sector` is unset in `smr.inc`.

smrealms/smr,smrealms/smr,hemberger/smr,hemberger/smr,smrealms/smr,hemberger/smr,hemberger/smr