fix broken sql in activity admin (#506)

* fix broken sql in activity admin
* pre-select customer for existing activities

src/Form/ActivityEditForm.php

@@ -59,6 +59,7 @@ class ActivityEditForm extends AbstractType
                 'query_builder' => function (CustomerRepository $repo) use ($customer) {
                     return $repo->builderForEntityType($customer);
                 },
+                'data' => $customer ? $customer : null,
                 'required' => false,
                 'mapped' => false,
                 'attr' => [

src/Repository/ActivityRepository.php

@@ -206,7 +206,9 @@ class ActivityRepository extends AbstractRepository
             $qb->orderBy('a.project', 'ASC');
         }
 
-        $qb->andWhere($or);
+        if ($or->count() > 0) {
+            $qb->andWhere($or);
+        }
 
         return $this->getBaseQueryResult($qb, $query);
     }