00:00:47.915 hudson.plugins.git.GitException: Could not checkout null with start point 3a7a46bb869eff4f16b2974d8f3dba7f56ce27a8

We are trying to analyse this situation for quite some time now - but we honestly have no clue.

This situation is sometimes triggered because of force pushes to branches.
Sometimes it happens because of other branches being merged into master.

A workaround is to create a new branch and a new pull request. As soon as the job is executed on this new pull request (which holds the identical commits) the job executes just fine.

Soometimes is also helps to not touch the branch for days and simply retrigger the execution.