[JENKINS-52264] Avoid empty environment injection from configuration

[Alex-Vol]

Fix empty environment issue in docker exec use case.

[jchauncey]

I'm running in to the same issue that this pr is attempting to fix so I want to build it locally to deploy it to our jenkins server in the meantime. However, Im having issues:

[ERROR] java.nio.file.NoSuchFileException: projects/jenkinsci/docker-workflow-plugin/target/classes/META-INF/annotations/hudson.Extension
[INFO] 1 error

[jchauncey]

Nevermind I just downloaded the hpi from the incrementals.

[jchauncey]

Ok I'm still seeing the following:

13:06:43 invalid argument "=" for "-e, --env" flag: invalid environment variable: =
13:06:43 See 'docker exec --help'.

[jchauncey]

Ok I figured out my issue and was able to fix it without this plugin.

Go to Manage Jenkins -> Configure System there will be an empty environment variable in the Global Properties section. If you remove that everything should work

[albertsj1]

Why in the world is this not merged yet? Such a small and simple fix to eliminate a very confusing and annoying problem. Please merge this so it can get into the next release. Thanks

[keijohyttinen]

This fix is very much needed as e.g. our optional but empty jenkins parameters will be empty env variables -> trigger the problem

[JungPhilipp]

Also waiting for this fix. Any chance this will be merged soon?

[Alex-Vol-SV]

Rebased to latest and cleaned up unintended whitespace changes.

[Alex-Vol-SV]

Could the maintainers of this plugin merge this simple pull request?