Before this change, if a user left a string value in a m2m_tags
and removed it afterward without selecting a tag, the update method
of Many2XAutoComplete would be called with false.
As the update method for m2m_tags expects a record or record list
this caused a traceback.
The fix is to simply skip the update in that case.
task-3109811
closesodoo/odoo#110123
X-original-commit: 14f314feb7594dc888de6af4e4ad23a948044854
Signed-off-by: Warnon Aurélien (awa) <awa@odoo.com>