Malformed HTML causing docx export to fail

[sentry-io]

Also reported by a user and manually verified:

https://opencasebook.org/casebooks/8825-contracts/

Sentry Issue: H2O-BA

ValueError: Invalid tag name 'http:'
(35 additional frame(s) were not displayed)
...
  File "src/lxml/sax.py", line 141, in lxml.sax.ElementTreeContentHandler.startElement
  File "src/lxml/sax.py", line 117, in lxml.sax.ElementTreeContentHandler.startElementNS
  File "src/lxml/etree.pyx", line 3153, in lxml.etree.SubElement
  File "src/lxml/apihelpers.pxi", line 179, in lxml.etree._makeSubElement
  File "src/lxml/apihelpers.pxi", line 1754, in lxml.etree._tagValidOrRaise

[lizadaly]

Corrected in the DB for this case