bug introduced in JENKINS-42443

https://github.com/jenkinsci/jenkins/commit/ed329d1088c164df560b9299cd9096ae76519418#diff-11b7f44b11e4a3dbf03e0baff633eb44R8

findFollowingTR(listBox, "validation-error-area") looks for first parent TR tag, which could be not the one that should be used (the one from <f:entry>) that causes js error

Uncaught TypeError: Cannot read property 'firstChild' of undefined
at updateListBox (select.js:8)
at select.js:79
at h (hudson-behavior.js:1295)
at refillOnChange (hudson-behavior.js:1310)
at select.js:77
at Array.forEach (<anonymous>)
at behavior.js:111
at Array.forEach (<anonymous>)
at behavior.js:107
at Array.forEach (<anonymous>)

which causes dropdown not to be populated 

example jelly which doesn't in jenkins 2.50+

https://github.com/jenkinsci/jclouds-plugin/blob/936aed28def5f2434dbdaaa72d260aadd3f623da/jclouds-plugin/src/main/resources/jenkins/plugins/jclouds/compute/UserData/config.jelly