Error: 500 addr is not a string

Hi, I am trying to validate an SVG file and am encountering a persistent
error.  The file is located here:
https://commons.wikimedia.org/wiki/File:Basket_of_flowers.svg .  When I
attempt to validate it, whether by uploading the file or copying and
pasting the content into the validator, I get an error that states "500
addr is not a string."  I have searched your database and searched the web
for this error message, and have found nothing on it (literally: 0 search
results).  The image looks like it is rendering correctly in my browser
(Firefox) but I am interested in also having it validated in order to
ensure it will also work across different platforms.  Any ideas what "500
addr is not a string" means??  Please let me know if so.  Thank you!