Corrected bad check for database config

lib/php/classes/Database.php

@@ -5,7 +5,7 @@
         private $statement;
 
         public function __construct ( $config ) {
-            if ( $config && $config [ 'host' ] && $config [ 'username' ] && $config [ 'password' ] && $config [ 'name' ] && $config [ 'port' ] ) {
+            if ( isset ( $config ) && isset ( $config [ 'host' ] ) && isset ( $config [ 'username' ] ) && isset ( $config [ 'password' ] ) && isset ( $config [ 'name' ] ) && isset ( $config [ 'port' ] ) ) {
                 $this->config = $config;
             }
             else {