[FIX] mass_mailing: hide action buttons in 'sending' state

Before this commit:
In a mass mailing, the action buttons such as 'put_in_queue' (Send) and
'action_schedule_date' (Schedule) are visible in 'sending' state, which
is not correct because users should not be able re-launch it in sending
state.

After this commit:
We hide those action button in 'sending' state to prevent user from
re-launching mass mailing when it's already in queue.

Task-Id : 2469352

closes odoo/odoo#67031

Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>

addons/mass_mailing/views/mailing_mailing_views.xml

@@ -56,9 +56,9 @@
             <field name="arch" type="xml">
                 <form string="Mailing">
                     <header style="min-height:31px;">
-                        <button name="action_put_in_queue" type="object" attrs="{'invisible': [('state', 'in', ('in_queue', 'done'))]}" class="oe_highlight" string="Send"
+                        <button name="action_put_in_queue" type="object" attrs="{'invisible': [('state', 'in', ('in_queue', 'sending', 'done'))]}" class="oe_highlight" string="Send"
                             confirm="This will send the email to all recipients. Do you still want to proceed ?"/>
-                        <button name="action_schedule" type="object" attrs="{'invisible': [('state', 'in', ('in_queue', 'done'))]}" class="btn-secondary" string="Schedule"/>
+                        <button name="action_schedule" type="object" attrs="{'invisible': [('state', 'in', ('in_queue', 'sending', 'done'))]}" class="btn-secondary" string="Schedule"/>
                         <button name="action_test" type="object" class="btn-secondary" string="Test"/>
                         <button name="action_cancel" type="object" attrs="{'invisible': [('state', '!=', 'in_queue')]}" class="btn-secondary" string="Cancel"/>
                         <button name="action_retry_failed" type="object" attrs="{'invisible': ['|', ('state', '!=', 'done'), ('failed', '=', 0)]}" class="oe_highlight" string="Retry"/>