Show Solution doesn't work if Sound effects is disabled

Issue was reported in https://h5p.org/node/113857

Steps to recreate the issue:
1. Create a Single Choice set (Stand alone or embeded in Column, Question Set and Course Presentation)
2. Uncheck "Enable Sound Effects"
3. Answer some questions wrong
4. Click on Show Solution button - Nothing happens.

Below are 2 test contents:
Embeded in CP
Stand Alone