[FIX] odoo: Traceback when creating a new contact

Steps to reproduce the bug:

- Let's consider a new instance with default installed language 'en_US'
- Install CRM
- Activate a second language (e.g. en_GB)
- Set that language in all users
- Inactivate default language 'en_US'
- Reset the language of your current user (no value)
- Go to contact and try to create a new one

Bug:

A traceback was raised because the lang en_US did not exist.

PS: Forcing the user to set a language ensures that this fallback
will never occur anymore.

opw:2267711

closes odoo/odoo#53375

Signed-off-by: Simon Goffin (sig) <sig@openerp.com>

odoo/addons/base/views/res_users_views.xml

@@ -215,7 +215,7 @@
                                         <field name="active" invisible="1"/>
                                         <label for="lang" />
                                         <div class="o_row">
-                                            <field name="lang"/>
+                                            <field name="lang" required="1"/>
                                             <button
                                                 type="action"
                                                 name="%(base.res_lang_act_window)d"
@@ -353,7 +353,7 @@
                         <group>
                             <label for="lang"/>
                             <div class="o_row">
-                                <field name="lang" readonly="0"/>
+                                <field name="lang" required="1" readonly="0"/>
                                 <button
                                     type="action"
                                     name="%(base.res_lang_act_window)d"