I observed this in older versions of Hudson, from February 8th I think. Have not
yet confirmed in a more recent build.

When the Javadoc basedir does not exist by the end of the build (because the
build failed before it got to that point), an exception is thrown at the end of
the build:

Publishing Javadoc
FATAL: Unable to copy Javadoc from
http://deadlock.nbextras.org/hudson/job/javadoc-nbms/ws/apisupport/apidocs/build/javadoc
to /hudson/workdir/jobs/javadoc-nbms/javadoc
hudson.util.IOException2: Failed to copy
http://deadlock.nbextras.org/hudson/job/javadoc-nbms/ws/apisupport/apidocs/build/javadoc/**/*
to /hudson/workdir/jobs/javadoc-nbms/javadoc
at hudson.FilePath$18.invoke(FilePath.java:586)
at hudson.FilePath$18.invoke(FilePath.java:553)
at hudson.FilePath.act(FilePath.java:191)
at hudson.FilePath.copyRecursiveTo(FilePath.java:553)
at hudson.FilePath.copyRecursiveTo(FilePath.java:539)
at hudson.tasks.JavadocArchiver.perform(JavadocArchiver.java:56)
at hudson.model.Build$RunnerImpl.post(Build.java:135)
at hudson.model.Run.run(Run.java:544)
at hudson.model.Build.run(Build.java:99)
at hudson.model.Executor.run(Executor.java:61)
Caused by:
http://deadlock.nbextras.org/hudson/job/javadoc-nbms/ws/apisupport/apidocs/build/javadoc
not found.
at
org.apache.tools.ant.types.AbstractFileSet.getDirectoryScanner(AbstractFileSet.java:342)
at org.apache.tools.ant.taskdefs.Copy.execute(Copy.java:395)
at hudson.FilePath$18.invoke(FilePath.java:583)
... 9 more

It seems that there is no check that the basedir exists?