Unclear error in lxml (may be able to be improved in pykeepass)

[Poikilos]

Occurs when search is blank.

Traceback (most recent call last):
  File "/home/owner/git/linux-preinstall/utilities/diffkeepass.py", line 378, in <module>
    sys.exit(main())
  File "/home/owner/git/linux-preinstall/utilities/diffkeepass.py", line 334, in main
    compare_keepass(
  File "/home/owner/git/linux-preinstall/utilities/diffkeepass.py", line 148, in compare_keepass
    entry1 = kp1.find_entries(title=entry2.title, first=True)
  File "/home/owner/.local/lib/python3.10/site-packages/pykeepass/pykeepass.py", line 516, in find_entries
    res = self._find(prefix, entry_xp, path=path, tree=group, **kwargs)
  File "/home/owner/.local/lib/python3.10/site-packages/pykeepass/pykeepass.py", line 399, in _find
    res = self._xpath(
  File "/home/owner/.local/lib/python3.10/site-packages/pykeepass/pykeepass.py", line 321, in _xpath
    elements = tree.xpath(
  File "src/lxml/etree.pyx", line 2311, in lxml.etree._ElementTree.xpath
  File "src/lxml/xpath.pxi", line 357, in lxml.etree.XPathDocumentEvaluator.__call__
  File "src/lxml/xpath.pxi", line 225, in lxml.etree._XPathEvaluatorBase._handle_result
lxml.etree.XPathEvalError: Invalid predicate

workaround:

-        if not entry1:
+        if not entry1 and entry2.title:
            entry1 = kp1.find_entries(title=entry2.title, first=True)

• also avoid other uses of None in find_entries*