[Export][person] Fixed: error and more precision on household

composition

A filter and two aggregators create a join between composition and
household, but with a parameter at different date.

Each aggregator and filter now have a custom alias, to allow to set this
date parameter on each join.

src/Bundle/ChillMainBundle/Export/ExportManager.php

@@ -536,8 +536,8 @@ class ExportManager
                     . 'an ExportInterface.');
         }
 
-        if (null === $centers || [] === $centers) {
-            // we want to try if at least one center is reachable
+        if (null === $centers || [] !== $centers) {
+            // we want to try if at least one center is reachabler
             return [] !== $this->authorizationHelper->getReachableCenters(
                 $this->user,
                 $role