[Bug report] saving (output) throws errors

[rapatapa]

Basic information

• Operating System: Windows10
• Calibre Version: 7.13
• Plugin Version: 2.3.5
• Plugin Installation: From Calibre

Describe the bug
Translating from epub is OK (Translation completed.), but saving (output) throws errors.

══════════════════════════════════════
Original: Ali Parandeh
┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈
Translation (Cached): Ali Parandeh
══════════════════════════════════════
Time consuming: 0.02 minutes
Translation completed.
Traceback (most recent call last):
File "runpy.py", line 198, in _run_module_as_main
File "runpy.py", line 88, in _run_code
File "site.py", line 83, in
File "site.py", line 78, in main
File "site.py", line 50, in run_entry_point
File "calibre\utils\ipc\worker.py", line 215, in main
File "calibre\utils\ipc\worker.py", line 150, in arbitrary_n
File "calibre_plugins.ebook_translator.lib.conversion", line 242, in convert_item
File "calibre_plugins.ebook_translator.lib.conversion", line 86, in convert_book
File "calibre\ebooks\conversion\plumber.py", line 1305, in run
File "calibre_plugins.ebook_translator.lib.conversion", line 74, in convert
File "calibre_plugins.ebook_translator.lib.element", line 683, in add_translations
File "calibre_plugins.ebook_translator.lib.element", line 269, in add_translation
File "src/lxml/etree.pyx", line 1655, in lxml.etree.__ContentOnlyElement.set
File "src/lxml/etree.pyx", line 1651, in lxml.etree.__ContentOnlyElement._raiseImmutable
TypeError: this element does not have children or attributes

Expected behavior
Saving the translated text in pdf or other format (I tried).