fix SourceManager constructor

Service/SourceManager.php

@@ -24,8 +24,11 @@ class SourceManager {
     public function __construct(Container $container) {
         $this->container = $container;
         $em = $this->container->get('doctrine')->getManager();
+        $im = $this->container->get('dj3c1t_app.install_manager');
         try {
-            $this->sourceRepo = $em->getRepository("Dj3c1tSourceMLBundle:Source");
+            if($im->isInstalled()) {
+                $this->sourceRepo = $em->getRepository("Dj3c1tSourceMLBundle:Source");
+            }
         }
         catch (\Exception $e) {
         }