Reduced technical debts

Link to the issues in SonarQube:

1. Either remove this useless object instantiation of "Splashscreen" or use it

2. Either remove this useless object instantiation of "ErrorSplashscreen" or use it

3. Either remove this useless object instantiation of "Splashscreen" or use it

4. Replace this "switch" statement with "if" statements to increase readability.

5. Either remove this useless object instantiation of "ErrorSplashscreen" or use it

6. Either remove this useless object instantiation of "ErrorSplashscreen" or use it

7. Either remove this useless object instantiation of "ErrorSplashscreen" or use it

8. Either remove this useless object instantiation of "ErrorSplashscreen" or use it

9. Merge this if statement with the nested one.

10. Merge this if statement with the nested one.

11. Add a "default" clause to this "switch" statement.

12. Add a "default" clause to this "switch" statement.

The missing 15mins of debts where fixed in another merge/commit, but were assigned to me before.