SVG Text NG: Fix null pointer dereference in SVGObjectPainter::ApplyPaintResource()

layout_object_ can be a LayoutSVGRoot, and it seems <svg> doesn't have
an SVGElementResourceClient in this case.

Bug: 1247153
Change-Id: I9f7b8bd276c2f5c54e1737a1e3d486a946bf4250
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3144752


Auto-Submit: Kent Tamura <tkent@chromium.org>
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Commit-Queue: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/main@{#919122}