[FIX] qweb: fix overlapping multi-class in t-att-class

Previously, if two attributes in t-att-class shared some classes, their
presence would be determined by the last attribute declared, instead of
being present if any attribute containing it evaluates to true. This
commit fixes that.

tests/qweb/__snapshots__/qweb_t_att.test.ts.snap

@@ -27,3 +27,31 @@ exports[`qweb t-att t-att-class with multiple classes 2`] = `
     return vn4;
 }"
 `;
+
+exports[`qweb t-att t-att-class with multiple classes, some of which are duplicate 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"test\\"
+    let utils = this.constructor.utils;
+    let scope = Object.create(context);
+    let h = this.h;
+    let _1 = utils.toClassObj({'a b c':scope['value'],'a b d':!scope['value']});
+    let c2 = [], p2 = {key:2,class:_1};
+    let vn2 = h('div', p2, c2);
+    return vn2;
+}"
+`;
+
+exports[`qweb t-att t-att-class with multiple classes, some of which are duplicate 2`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"test\\"
+    let utils = this.constructor.utils;
+    let scope = Object.create(context);
+    let h = this.h;
+    let _3 = utils.toClassObj({'a b c':scope['value'],'a b d':!scope['value']});
+    let c4 = [], p4 = {key:4,class:_3};
+    let vn4 = h('div', p4, c4);
+    return vn4;
+}"
+`;

tests/qweb/qweb_t_att.test.ts

@@ -24,4 +24,13 @@ describe("qweb t-att", () => {
       '<div class="a b c"></div>'
     );
   });
+
+  test("t-att-class with multiple classes, some of which are duplicate", () => {
+    expect(render(`<div t-att-class="{'a b c': value, 'a b d': !value}" />`, { value: true })).toBe(
+      '<div class="a b c"></div>'
+    );
+    expect(render(`<div t-att-class="{'a b c': value, 'a b d': !value}" />`, { value: false })).toBe(
+      '<div class="a b d"></div>'
+    );
+  });
 });