ZP-795 remove useless assignment.

Released under the Affero GNU General Public License (AGPL) version 3.

src/lib/default/backend.php

@@ -303,7 +303,7 @@ abstract class Backend implements IBackend {
         }
         if (isset($this->stateStorage)) {
             try {
-                $this->storage_state = ZPush::GetDeviceManager()->GetStateManager()->SetBackendStorage($this->stateStorage, StateManager::BACKENDSTORAGE_STATE);
+                ZPush::GetDeviceManager()->GetStateManager()->SetBackendStorage($this->stateStorage, StateManager::BACKENDSTORAGE_STATE);
             }
             catch (StateNotYetAvailableException $snyae) { }
             catch(StateNotFoundException $snfe) { }