[FIX] base_address_city: lost information when creating Partner from Lead

Have a Lead with the contact informations (Customer Name, Street,
Street 2, City, State, ZIP, Country) completed in the 'Followup' page.

Before this commit, when the base_adress_city module was installed, the
informations of the City, State and ZIP where lost when we try to create
a new Partner from the Lead.

Now, the informations are present in the Partner form; furthermore if
the country allows enforce cities, the information is also present in
the enforce city form.

OPW-1932018

closes odoo/odoo#30644

addons/base_address_city/models/res_partner.py

@@ -15,9 +15,10 @@ class Partner(models.Model):
 
     @api.onchange('city_id')
     def _onchange_city_id(self):
-        self.city = self.city_id.name
-        self.zip = self.city_id.zipcode
-        self.state_id = self.city_id.state_id
+        if self.city_id:
+            self.city = self.city_id.name
+            self.zip = self.city_id.zipcode
+            self.state_id = self.city_id.state_id
 
     @api.model
     def _fields_view_get_address(self, arch):
@@ -37,7 +38,10 @@ class Partner(models.Model):
                     }"
                 />
                 <field name='city_id' placeholder="%(placeholder)s" string="%(placeholder)s"
-                    context="{'default_country_id': country_id}"
+                    context="{'default_country_id': country_id,
+                              'default_name': city,
+                              'default_zipcode': zip,
+                              'default_state_id': state_id}"
                     domain="[('country_id', '=', country_id)]"
                     attrs="{
                         'invisible': [('country_enforce_cities', '=', False)],