That error happens on all servers. You are just happening to crash right after it since plugins are the next thing to load after it displays.
Make sure that your server is updated as well. The latest D2Fixups (1.6) only works with servers from after this past week's update (the one that added solo queue).
Server is up to date. Any way to figure out why it's crashing there? -condebug doesn't print that early, and the plugins are all up to date.
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