Since rev. 755a8d815a, it crashed when the user tried to open an
x2many record in form view (thus in a dialog), if there was a
chatter in that form's arch.
This was because the wrong viewType was used (for instance, list
or kanban instead of form), to look into fieldsInfo, and thus the
chatter fields couldn't be found.
opw 1891378
opw 1892520
opw 1893100
closes odoo/odoo#27844