Seems something broke with the forums database.
The *.png image file is no longer loadable here.
Seems the *.graphml became inacessible too.
Hmm … I can reupload the image screencap but not the *.graphml.
The file extension is invalid.
*.svg is blocked too.
Sorry about that. The directory where images generated by those file types got moved somehow. The directory has been moved back to where it belongs so the images should now display. I have not tested whether graphml or svg files can again be uploaded.