[Backup] Added null check for Restore backup uri

app/src/main/java/code/name/monkey/retromusic/fragments/backup/BackupFragment.kt

@@ -48,9 +48,11 @@ class BackupFragment : Fragment(R.layout.fragment_backup), BackupAdapter.BackupC
         backupViewModel.loadBackups()
         val openFilePicker = registerForActivityResult(ActivityResultContracts.OpenDocument()) {
             lifecycleScope.launch(Dispatchers.IO) {
+                it?.let {
                     backupViewModel.restoreBackup(requireActivity(), requireContext().contentResolver.openInputStream(it))
                 }
             }
+        }
         binding.createBackup.setOnClickListener {
             showCreateBackupDialog()
         }