EasySlides importer causes traceback on unexpected chars

Reported here, includes example file: https://support.openlp.org/scp/tickets.php?id=3507

If an unexpected (control) char sneaks into the song data, OpenLP throws a traceback:

--- Exception Traceback ---
Traceback (most recent call last):
  File "openlp\core\ui\wizard.py", line 216, in on_current_id_changed
  File "openlp\plugins\songs\forms\songimportform.py", line 351, in
perform_wizard
  File "openlp\plugins\songs\lib\importers\easyslides.py", line 50, in
do_import
  File "lxml.etree.pyx", line 3310, in lxml.etree.parse
(src\lxml\lxml.etree.c:72517)
  File "parser.pxi", line 1791, in lxml.etree._parseDocument
(src\lxml\lxml.etree.c:105979)
  File "parser.pxi", line 1817, in lxml.etree._parseDocumentFromURL
(src\lxml\lxml.etree.c:106278)
  File "parser.pxi", line 1721, in lxml.etree._parseDocFromFile
(src\lxml\lxml.etree.c:105277)
  File "parser.pxi", line 1122, in lxml.etree._BaseParser._parseDocFromFile
(src\lxml\lxml.etree.c:100227)
  File "parser.pxi", line 580, in
lxml.etree._ParserContext._handleParseResultDoc
(src\lxml\lxml.etree.c:94350)
  File "parser.pxi", line 690, in lxml.etree._handleParseResult
(src\lxml\lxml.etree.c:95786)
  File "parser.pxi", line 620, in lxml.etree._raiseParseError
(src\lxml\lxml.etree.c:94853)
  File "<string>", line None
lxml.etree.XMLSyntaxError: xmlParseCharRef: invalid xmlChar value 11, line
17081, column 62