Clear contents of log_text after successfull backup (borgbase#1626)

Currently the label `logText` is not cleared after a borg command finished. When creating a backup the label will show the path of the last backuped file even after backup completion.

This changes that and clears `logText` after the backup.

* src/vorta/borg/create.py (BorgCreateJob.process_result)

---------

Co-authored-by: yfprojects <62463991+real-yfprojects@users.noreply.github.com>

src/vorta/borg/create.py

@@ -49,6 +49,7 @@ def process_result(self, result):
                     ).format(LOG_DIR.as_uri())
                 )
             else:
+                self.app.backup_log_event.emit('', {})
                 self.app.backup_progress_event.emit(f"[{self.params['profile_name']}] {self.tr('Backup finished.')}")
 
     def progress_event(self, fmt):