PDOException: SQLSTATE[23000]: Integrity constraint violation: 1048 Column 'hostname' cannot be null:

I keep seeing the following in the logs after the cron runs. I have searched related issues but I don't seem to have the same problem as everyone else. Can anybody point me in the direction of clearing this up.

PDOException: SQLSTATE[23000]: Integrity constraint violation: 1048 Column 'hostname' cannot be null: INSERT INTO {sessions} (sid, ssid, uid, cache, hostname, session, timestamp) VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2, :db_insert_placeholder_3, :db_insert_placeholder_4, :db_insert_placeholder_5, :db_insert_placeholder_6); Array ( [:db_insert_placeholder_0] => fofPnJmj9EcI7Mns1C5wxuES05hgPV-WpqJkKMBWb6c [:db_insert_placeholder_1] => [:db_insert_placeholder_2] => 0 [:db_insert_placeholder_3] => 0 [:db_insert_placeholder_4] => [:db_insert_placeholder_5] => messages|a:1:{s:5:"error";a:3:{i:0;s:261:"<em class="placeholder">Notice</em>: Undefined index: REMOTE_ADDR in <em class="placeholder">ip_address()</em> (line <em class="placeholder">2852</em> of <em class="placeholder">/home/content/16/11956916/html/test.gen6floralsupply/includes/bootstrap.inc</em>).";i:1;s:472:"<em class="placeholder">Warning</em>: session_start() [<a href='function.session-start'>function.session-start</a>]: Cannot send session cookie - headers already sent by (output started at /home/content/16/11956916/html/test.gen6floralsupply/includes/bootstrap.inc:3340) in <em class="placeholder">drupal_session_start()</em> (line <em class="placeholder">287</em> of <em class="placeholder">/home/content/16/11956916/html/test.gen6floralsupply/includes/session.inc</em>).";i:2;s:476:"<em class="placeholder">Warning</em>: session_start() [<a href='function.session-start'>function.session-start</a>]: Cannot send session cache limiter - headers already sent (output started at /home/content/16/11956916/html/test.gen6floralsupply/includes/bootstrap.inc:3340) in <em class="placeholder">drupal_session_start()</em> (line <em class="placeholder">287</em> of <em class="placeholder">/home/content/16/11956916/html/test.gen6floralsupply/includes/session.inc</em>).";}} [:db_insert_placeholder_6] => 1383296401 ) in _drupal_session_write() (line 209 of /home/content/16/11956916/html/test.gen6floralsupply/includes/session.inc).