Error with https://fsis.site/blog/index.xml

[fsi]

URL: https://fsis.site/blog/index.xml
Status: 200
Error: Cannot read property '0' of null

https://validator.w3.org/feed/ says it's a valid RSS feed, and it's pretty much a vanilla hugo install anyway.

Running with --debug produces the following traceback:

$ wm https://fsis.site/blog/index.xml --debug
limit = 10
send = false
Fetching https://fsis.site/blog/index.xml
Content is RSS
entries = 10
TypeError: Cannot read property '0' of null
    at getName (/home/fsi/.npm-packages/lib/node_modules/@remy/webmention/node_modules/css-what/index.js:97:36)
    at parseSelector (/home/fsi/.npm-packages/lib/node_modules/@remy/webmention/node_modules/css-what/index.js:152:13)
    at parse (/home/fsi/.npm-packages/lib/node_modules/@remy/webmention/node_modules/css-what/index.js:82:13)
    at compileUnsafe (/home/fsi/.npm-packages/lib/node_modules/@remy/webmention/node_modules/css-select/lib/compile.js:31:14)
    at select (/home/fsi/.npm-packages/lib/node_modules/@remy/webmention/node_modules/css-select/index.js:18:49)
    at CSSselect (/home/fsi/.npm-packages/lib/node_modules/@remy/webmention/node_modules/css-select/index.js:41:9)
    at initialize.exports.find (/home/fsi/.npm-packages/lib/node_modules/@remy/webmention/node_modules/cheerio/lib/api/traversing.js:40:21)
    at initialize.module.exports (/home/fsi/.npm-packages/lib/node_modules/@remy/webmention/node_modules/cheerio/lib/cheerio.js:86:18)
    at new initialize (/home/fsi/.npm-packages/lib/node_modules/@remy/webmention/node_modules/cheerio/lib/static.js:29:20)
    at initialize (/home/fsi/.npm-packages/lib/node_modules/@remy/webmention/node_modules/cheerio/lib/static.js:26:14)
    at $ (/home/fsi/.npm-packages/lib/node_modules/@remy/webmention/lib/rss/dom.js:49:14)
    at base.map (/home/fsi/.npm-packages/lib/node_modules/@remy/webmention/lib/links.js:14:18)
    at items.map (/home/fsi/.npm-packages/lib/node_modules/@remy/webmention/lib/rss/dom.js:23:16)
    at Array.map (<anonymous>)
    at Object.map (/home/fsi/.npm-packages/lib/node_modules/@remy/webmention/lib/rss/dom.js:22:25)
    at links (/home/fsi/.npm-packages/lib/node_modules/@remy/webmention/lib/links.js:13:6)