Promotion condition script fails only when build is running #2847

I've got a very simple promotion defined which is used to re-trigger the configuration. The promotion is defined high and inherited downward, and needs to only be available on leaf configs (no children).

The condition script is simply:


return configuration.getChildren().size() == 0

The page renders fine if you visit a completed build, but if you go to a build in-flight, an exception is displayed:


Failed to evaluate the expression:
mvel: return configuration.getChildren().size() == 0

I've tried variations of the script including verifying that the objects being referenced are not null, but I always get the same result. Is there some way to avoid this?