When adding a "Copy Artifact from another project" step in the promotion process in a Job Template, the server raises a NullPointerException when processing the following request:

http://localhost:8083/job/test-template/descriptorByName/hudson.plugins.copyartifact.CopyArtifact/checkProjectName?value=

The method doCheckProjectName in the CopyArtifact assume that the @AncestorInPath is not null which is a bug.

Source code here: https://github.com/jenkinsci/copyartifact-plugin/blob/b17cbb4036e9045472cbb1b35c4b8e7ef712f375/src/main/java/hudson/plugins/copyartifact/CopyArtifact.java#L582

How to reproduce:

• Create a Job Template "test-job" at the root
• Tick "Define Promotion Process"
• "Copy Artifact from another project" action
• An ERROR link appears

Note: This issue does not block the functionality and this error can be ignored. Specifying an existing project and saving the configuration will make this error disappears.