Defender - ignored a file and now my site is broken (error 500)

My entire site is broken and inaccessible. This is what I did: I installed WPMU, Installed Defender, set it up. I got to a file warning about an error log - it said that the file could be safely ignored, but if I deleted it, to be sure to back up my site first. I clicked Ignore. Now my site is inaccessible.

Please advise. I have not been backing up this site!