Btw I found now the solution. If you have the same error as I had, do the following:
1.) Click on the extension "Tetris"
2.) Deactive there the property "Enable music" and set None for Background music. Now it works for me 
Btw I found now the solution. If you have the same error as I had, do the following:
1.) Click on the extension "Tetris"
2.) Deactive there the property "Enable music" and set None for Background music. Now it works for me