thank you @karolus and @fpy, your help is greatly appreciated! 
By the way guys, I have not marked anything as a solution since your help with the code was not related to LibreOffice/Scriptforge asking to enable Java environment. It is also not confirmed to be a bug, so I haven’t marked mikekaganski’s answer as a solution either. In case I am wrong, please let me know.
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In case you are interested, here is the reported bug
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EDIT: It has been confirmed as a bug at the report page, so I mark @mikekaganski answer as solution. Thank you very much to all of you!