SCORM activity description is mandatory on edition, not on creation

The status of the description field for SCORM activities is not inconsistent:

• when adding SCORM content with a drag&drop of the zip package onto the course, the activity is created and available with an empty description
• when editing a SCORM activity, the description has to be filled.

Suggested change: make the description non mandatory on edition. Unchanged SCORM activities may keep an empty description, there is no reason why it should be added when changing another field.