Error in table structure 'ports-state'

After commit #3309, poller write errors like this:

PHP Warning:  QDB - Insert failed. in /usr/local/www/observium/includes/dbFacile.php on line 81

PHP Warning:  QDB - Insert failed. in /usr/local/www/observium/includes/dbFacile.php on line 81

This is due to the fact that in file ports.inc.php (line 402) is an attempt to add data:

$insert = dbInsert(array('port_id' => $port['port_id']), 'ports-state');

But the structure of the table 'posts-state' does not allow an NULL field for the `ifInOctets_perc` and `ifOutOctets_perc`.

Attached patch for fix this.