[JENKINS-35993] Fix Blue Ocean button for when no context root
[JENKINS-35993] Fix Blue Ocean button for when no context root

jenkinsci/blueocean-plugin,tfennelly/blueocean-plugin,kzantow/blueocean-plugin,jenkinsci/blueocean-plugin,alvarolobato/blueocean-plugin,ModuloM/blueocean-plugin,jenkinsci/blueocean-plugin,alvarolobato/blueocean-plugin,ModuloM/blueocean-plugin,kzantow/blueocean-plugin,alvarolobato/blueocean-plugin,tfennelly/blueocean-plugin,ModuloM/blueocean-plugin,kzantow/blueocean-plugin,tfennelly/blueocean-plugin,tfennelly/blueocean-plugin,kzantow/blueocean-plugin,jenkinsci/blueocean-plugin,jenkinsci/blueocean-plugin,alvarolobato/blueocean-plugin,ModuloM/blueocean-plugin