[FIX] web: pager offset in list interprets 0 as falsy when it shouldn't

If a view with groups and pager, going next then previous (back to the 0
offset) doesn't work.

The pager offset and limit were used in an conditional expression.
If the value was 0, it was considered falsy and set to a default value
while the 0 was actually a valid and expected value.

closes odoo/odoo#101314

X-original-commit: 5c9173241dbe55007c3a84fe078d21ea733e9046
Signed-off-by: Julien Mougenot (jum) <jum@odoo.com>
Signed-off-by: Simon Genin (ges@odoo) <ges@odoo.com>

addons/web/static/src/views/relational_model.js

@@ -2223,8 +2223,8 @@ export class DynamicGroupList extends DynamicList {
     }
 
     async load(params = {}) {
-        this.limit = params.limit || this.limit;
-        this.offset = params.offset || this.offset;
+        this.limit = params.limit === undefined ? this.limit : params.limit;
+        this.offset = params.offset === undefined ? this.offset : params.offset;
         /** @type {[Group, number][]} */
         const previousGroups = this.groups.map((g, i) => [g, i]);
         this.groups = await this._loadGroups();

addons/web/static/tests/views/list_view_tests.js

@@ -15045,4 +15045,20 @@ QUnit.module("Views", (hooks) => {
         assert.containsN(target, ".o_data_row:first-child td.o_list_button", 1);
         await click(target, ".o_data_row:first-child td.o_list_button");
     });
+
+    QUnit.test("group by going to next page then back to first", async function (assert) {
+        await makeView({
+            type: "list",
+            resModel: "foo",
+            serverData,
+            arch: '<tree groups_limit="1"><field name="foo"/><field name="bar"/></tree>',
+            groupBy: ["bar"],
+        });
+
+        assert.deepEqual([...getPagerValue(target), getPagerLimit(target)], [1, 2]);
+        await pagerNext(target);
+        assert.deepEqual([...getPagerValue(target), getPagerLimit(target)], [2, 2]);
+        await pagerPrevious(target);
+        assert.deepEqual([...getPagerValue(target), getPagerLimit(target)], [1, 2]);
+    });
 });