[RavSinghChandan]

The matplotlib charts in the RapidFuzz documentation (docs/Usage/img/*.svg, 18 files) were minified, and the glyph of the space character was dropped while the <use xlink:href="#AG"/> that place it were kept. pdf.image() fails on all of them:

ValueError: use <Element '{http://www.w3.org/2000/svg}use' at 0x...> references nonexistent ref id #AG

Browsers draw nothing for such a <use> and render the rest of the chart, which here only loses the spaces between words. build_xref() now logs a warning ("Ignoring of nonexistent ref id #AG") and returns the empty group, as it already does for a <use> of a hidden element. A <use> without any href still raises, as test_bad_xref checks.

This changes test_missing_xref, which expected the ValueError: it now checks the warning, that the <use> draws nothing and that a shape after it is still drawn; it fails without the change. All 18 RapidFuzz charts now render. Changelog entry under 2.9.1 / Fixed.