[FIX] web: call _applyX2ManyChange with the correct viewtype

Have a one2many display records in a kanban subview,
which opens a form view when edited.
Edit a field displayed only on the form view.
A call to _applyX2ManyChange is done without giving it the viewtype argument,
therefore the fieldinfo is taken from the wrong view, traceback ensues.

opw 1914163

closes odoo/odoo#29607

addons/web/static/src/js/views/basic/basic_model.js

@@ -1937,7 +1937,7 @@ var BasicModel = AbstractModel.extend({
                     addDef = this._applyX2ManyChange(record, fieldName, {
                         operation: 'ADD_M2M',
                         ids: values
-                    });
+                    }, viewType);
                 }
                 if (removedIds.length) {
                     var listData = _.map(list.data, function (localId) {
@@ -1951,7 +1951,7 @@ var BasicModel = AbstractModel.extend({
                             }
                             return _.findWhere(listData, {res_id: resID}).id;
                         }),
-                    });
+                    }, viewType);
                 }
                 return $.when(addDef, removedDef);
         }

addons/web/static/tests/fields/relational_fields_tests.js

@@ -3357,6 +3357,46 @@ QUnit.module('relational_fields', {
         form.destroy();
     });
 
+    QUnit.test('widget many2many_checkboxes in a subview', function (assert) {
+        assert.expect(2);
+
+        var form = createView({
+            View: FormView,
+            model: 'partner',
+            data: this.data,
+            arch:'<form string="Partners">' +
+                    '<sheet>' +
+                        '<notebook>' +
+                            '<page string="Turtles">' +
+                                '<field name="turtles" mode="tree">' +
+                                    '<tree>' +
+                                        '<field name="id"/>' +
+                                    '</tree>' +
+                                '</field>' +
+                            '</page>' +
+                        '</notebook>' +
+                    '</sheet>' +
+            '</form>',
+            archs: {
+                'turtle,false,form': '<form>' +
+                    '<field name="partner_ids" widget="many2many_checkboxes"/>' +
+                '</form>',
+            },
+            res_id: 1,
+        });
+
+        form.$buttons.find('.o_form_button_edit').click();
+        form.$('.o_data_cell').click();
+        // edit the partner_ids field by (un)checking boxes on the widget
+        var $firstCheckbox = $('.modal .custom-control-input').first();
+        $firstCheckbox.click();
+        assert.ok($firstCheckbox.prop('checked'), "the checkbox should be ticked");
+        var $secondCheckbox = $('.modal .custom-control-input').eq(1);
+        $secondCheckbox.click();
+        assert.notOk($secondCheckbox.prop('checked'), "the checkbox should be unticked");
+        form.destroy();
+    });
+
     QUnit.test('embedded one2many with widget', function (assert) {
         assert.expect(1);