Fix null pointer after uploading backup file

app/src/main/java/com/todoroo/astrid/backup/BackupConstants.kt

@@ -49,8 +49,8 @@ object BackupConstants {
         return getTimestampFromFilename(file.name) ?: file.lastModified()
     }
 
-    fun getTimestamp(file: File): Long {
-        return getTimestampFromFilename(file.name) ?: file.modifiedTime.value
+    fun getTimestamp(file: File): Long? {
+        return getTimestampFromFilename(file.name) ?: file.modifiedTime?.value
     }
 
     fun getTimestamp(file: DocumentFile): Long {

app/src/main/java/org/tasks/drive/DriveInvoker.kt

@@ -144,7 +144,7 @@ class DriveInvoker @Inject constructor(
     companion object {
         private const val MIME_FOLDER = "application/vnd.google-apps.folder"
         private val DRIVE_FILE_COMPARATOR = Comparator<File> { f1, f2 ->
-            BackupConstants.getTimestamp(f2).compareTo(BackupConstants.getTimestamp(f1))
+            BackupConstants.getTimestamp(f2)!!.compareTo(BackupConstants.getTimestamp(f1)!!)
         }
     }
 }

app/src/main/java/org/tasks/jobs/DriveUploader.kt

@@ -40,12 +40,8 @@ class DriveUploader @WorkerInject constructor(
             val folder = getFolder() ?: return Result.failure()
             preferences.setString(R.string.p_google_drive_backup_folder, folder.id)
             drive.createFile(folder.id, uri)
-                    ?.let {
-                        preferences.setLong(
-                                R.string.p_backups_drive_last,
-                                BackupConstants.getTimestamp(it)
-                        )
-                    }
+                    ?.let(BackupConstants::getTimestamp)
+                    ?.let { preferences.setLong(R.string.p_backups_drive_last, it) }
             localBroadcastManager.broadcastPreferenceRefresh()
             if (inputData.getBoolean(EXTRA_PURGE, false)) {
                 drive