Exercises G26

Description:
The second challenge can not be chosen after completing level 17.

Test steps:
1.Open the game.
2.Chose one challenge.
3.Start playing until level 17 is completed.
4.Choose a second challenge.

Expected result:
After reaching level 17, the second challenge should be chosen.

Actual result:
After reaching level 17, the second challenge can not be chosen.