Fix not on fx thread error for custom entry types
Fix not on fx thread error for custom entry types

Revert change done in  #5423 because the actual code just opens the already loaded databases
at this point the databases are already loaded in a background thread

Siedlerchr/jabref,JabRef/jabref,JabRef/jabref,sauliusg/jabref,sauliusg/jabref,Siedlerchr/jabref,sauliusg/jabref,JabRef/jabref,Siedlerchr/jabref,JabRef/jabref,sauliusg/jabref,Siedlerchr/jabref