Resolve "Page figée après une permutation de sections"

Closes #3

See merge request !3

Resolve "Bobologie 2"

Closes #2

See merge request !2

Resolve "Bobologie 1"

Closes #1

See merge request !1

Merge branch '1-bobologie-1' of https://gitlab.univ-lorraine.fr/iena/course-format into 1-bobologie-1

* '1-bobologie-1' of https://gitlab.univ-lorraine.fr/iena/course-format:
  Checking that some variables exist before using it.

Merge branch '2-bobologie-2' of https://gitlab.univ-lorraine.fr/iena/course-format into 2-bobologie-2

* '2-bobologie-2' of https://gitlab.univ-lorraine.fr/iena/course-format:
  Fix sections header send twice in edit mode.