Skip DB backup on Postgres DB

src/NzbDrone.Core/Backup/BackupService.cs

@@ -186,11 +186,14 @@ namespace NzbDrone.Core.Backup
         }
 
         private void BackupDatabase()
+        {
+            if (_maindDb.DatabaseType == DatabaseType.SQLite)
             {
                 _logger.ProgressDebug("Backing up database");
 
                 _makeDatabaseBackup.BackupDatabase(_maindDb, _backupTempFolder);
             }
+        }
 
         private void BackupConfigFile()
         {