If the web console bundle gets restarted while a bundle is being updated in the BaseUpdateInstallerHelper thread and an exception happens during the update, the log message cannot be written causing a NullPointerException. This factually hides the actual problem.
The fix is to catch any exception when trying to log the message and just write the error to std err to at least get some indication of problems.
One such potential situation is failing to update the web console bundle itself (e.g. due to missing dependencies)