Merge pull request #878 from Virakal/master

Fix call on non-object in ping() with PDO wrapper

lib/Doctrine/DBAL/Connection.php

@@ -1597,7 +1597,7 @@ class Connection implements DriverConnection
         }
 
         try {
-            $this->query($this->platform->getDummySelectSQL());
+            $this->query($this->getDatabasePlatform()->getDummySelectSQL());
 
             return true;
         } catch (DBALException $e) {