The custom sidepanel on About Jenkins is broken (present but too narrow) between 970px and 1168px.

Works correctly in 2.339, broken in 2.340.

Works in incremental jenkins-war-2.340-rc32202.2a_d5073a_3946.war; broken in incremental jenkins-war-2.340-rc32206.5144035e5503.war; indicating from https://github.com/jenkinsci/jenkins/compare/2ad5073a3946...5144035e5503 that https://github.com/jenkinsci/jenkins/pull/6307 broke it.