"AWT-EventQueue-0" eror in 3D World Editor

I get the error AWT-EventQueue-0 while tring to expanding subtrees in World Editor and they dont expand so i cant change anything.

I was using 2019b and updated it to 2020a but still the same problem.

I tried to downgrade the version of Java but it didn't help. Does anybody know the solution? Thanks.

[Kerim Moral]

Problem is solved with changing my computer language to English.