fixing bug #4233 with the help of Jquery
fixing bug #4221 by preventing NullPointerException...
fixing bug #4219 by preventing NullPointerException...
However, origin of this exception is not yet identified
fixing bug #4225 by removing obsolete Javascript code
fixing bug #4219
management of fields of type file (file, image and video) is fixed when clone is used
another bug (recent regression) have been fixed when updating a form which contains a file
if this field were not updated, field was empty and file was lost !