BUG : title and long question

If someone doesn't put a Title for a question but fills the Question field (so : multiline, with potentially markup), it leads to an error : 

```
Parameter "titleToFind" for route "ujm_exercise_questions" must match ".+" ("some content
some content
some content" given) to generate a corresponding URL.
500 Internal Server Error - InvalidParameterException
```

Maybe title should be mandatory ?
