Created attachment 991776 [details]
Java error console (backtrace)
Description of problem:
There must be something else broken for you, which then leads to the NullPointerException of attachment 991776 [details]. There is some logging mechanism in LibreOffice's scripting framework that could be used to get more information about your true problem, if only that logging mechanism were not completely broken (cf. upstream <http://cgit.freedesktop.org/libreoffice/core/commit/?id=f1f6edaae13c9591e391d52856c31c6cdc303f3e> "Make LogUtils.getTrace actually work.")
I put a modified ScriptFramework.jar for Fedora 21 at <people.redhat.com/~sbergman/ScriptFramework.jar> that includes the above LogUtils.getTrace fix and enables the logging by default (so you'll see quite some output to stdout).
Thanks for the quick feedback!
and sorry for the trouble, but it could be an error on my part, because now it's working fine both with your jar and the original jar, though the nullpointer exception is printed anyway but should be harmless as the script window is now working.
so closing as WORKSFORME per comment 2