Fix bug where empty or null host connection parameter will still construct an...

Fix bug where empty or null host connection parameter will still construct an Oracle DSN instead of using dbname.

lib/Doctrine/DBAL/Driver/OCI8/Driver.php

@@ -50,7 +50,7 @@ class Driver implements \Doctrine\DBAL\Driver
     protected function _constructDsn(array $params)
     {
         $dsn = '';
-        if (isset($params['host'])) {
+        if (isset($params['host']) && $params['host'] != '') {
             $dsn .= '(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)' .
                    '(HOST=' . $params['host'] . ')';