#12718 fix error on signature package ums

pandora_console/update_manager_client/lib/UpdateManager/Client.php

@@ -2383,7 +2383,7 @@ class Client
 
             // Retrieve package from UMS.
             $this->notify(0, 'Downloading server update '.$version);
-            $this->post(
+            $package = $this->post(
                 [
                     'action'    => 'get_server_package',
                     'arguments' => ['version' => $version],
@@ -2407,6 +2407,11 @@ class Client
                 return false;
             }
 
+            if (empty($package) === true) {
+                $this->lastError = 'Error on Package from UMS';
+                return false;
+            }
+
             if ($this->propagateUpdates === true) {
                 $this->saveSignature(
                     $signature,