GDKPixbuf-based image exporters producing empty output with GDKPixbuf 2.44

I took this to Fedora first, because I'm still attempting to determine if it's a packaging bug or not. (It's not the packaging, it's GDKPixbuf 2.44.) The Fedora report is https://bugzilla.redhat.com/show_bug.cgi?id=2395533

With Fedora 43 Beta (graphviz-13.1.1-3.fc43.x86_64), which is based on GDKPixbuf 2.44 (gdk-pixbuf2-2.44.0-1.fc43.x86_64) and its new Glycin (Rust-based) image backend, we're seeing empty output from Dot commands that use -Tjpg:cairo:gdk, -Tpng:cairo:gdk, etc.

Other JPEG output formats like -Tjpg:cairo:gd, -Tjpg:cairo:devil, or -Tjpg:gd:gd are all unaffected.

The JPG situation is worse than for PNG, because -Tjpg:cairo:gdk is the default for -Tjpg. With PNG, -Tpng implies -Tpng:cairo:cairo which is unaffected.

Steps to reproduce

$ echo "graph G { a--b; }" | dot -Tjpg -o test.jpg
$ file test.jpg
test.jpg: empty
$ echo "graph G { a--b; }" | dot -Tpng:cairo:gdk -o test.png
$ file test.png
test.png: empty
$ echo "graph G { a--b; }" | dot -Tjpg:cairo:gd | file -
/dev/stdin: JPEG image data, JFIF standard 1.01, resolution (DPI), density 96x96, segment length 16, comment: "CREATOR: gd-jpeg v1.0 (using IJG JPEG v62), default quality", baseline, precision 8, 83x155, components 3
$ echo "graph G { a--b; }" | dot -Tpng | file -
/dev/stdin: PNG image data, 83 x 155, 8-bit/color RGBA, non-interlaced