NUL byte in <link> href confuses libxml2-lxml parser

[JustAnotherArchivist]

Via ArchiveBot job b4cobsdfap6j2kzjo3i4jwnsx:

wpull --recursive --no-verbose --no-parent --html-parser libxml2-lxml https://www.e-gov.am/gov-decrees/item/23174/

This recurses to wonderful URLs such as https://www.e-gov.am/gov-decrees/item/23174/1clip_themedata.thmx%22%20rel=%22themeData%22%20/%3E (and it only gets worse from there).

The page contains these three <link> tags with NUL bytes (^@):

<link href="file:///C:DOCUME~1MarineALOCALS~1Tempmsohtmlclip1^@1clip_filelist.xml" rel="File-List" />
<link href="file:///C:DOCUME~1MarineALOCALS~1Tempmsohtmlclip1^@1clip_themedata.thmx" rel="themeData" />
<link href="file:///C:DOCUME~1MarineALOCALS~1Tempmsohtmlclip1^@1clip_colorschememapping.xml" rel="colorSchemeMapping" />

This only happens with the libxml2-lxml parser; the html5lib parser handles it correctly, i.e. does not extract any extra URLs.

Tested on two machines, both with Python 3.6.10. One has lxml 4.4.2 and libxml2 2.9.4 with wpull 2.0.3, the other has lxml 4.6.2 and libxml2 2.9.10 with wpull The Blocking PR 393.