Exception in rendering!

Message: Cannot read property 'username' of null

TypeError: Cannot read property 'username' of null
    at <eval>:173:91555
    at Array.map (native)
    at b (<eval>:173:91494)
    at t.K.value (<eval>:47:27221)
    at t.K.value (<eval>:47:28848)
    at r (<eval>:110:7982)
    at K (<eval>:110:8242)
    at e.render (<eval>:110:9812)
    at e.read (<eval>:110:9550)
    at Object.Y.renderToString (<eval>:110:13823)