[FIX] qweb: do not capture current qweb instance in closure

it is not needed, and has a bad effect on globally registered templates.

src/qweb/qweb.ts

@@ -241,7 +241,7 @@ export class QWeb extends EventBus {
     this._processTemplate(elem);
     const template = {
       elem,
-      fn: (context, extra) => {
+      fn: function (this: QWeb, context, extra) {
         const compiledFunction = this._compile(name, elem);
         template.fn = compiledFunction;
         return compiledFunction.call(this, context, extra);

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

@@ -1118,6 +1118,21 @@ exports[`t-call (template calling t-call with t-if 1`] = `
 }"
 `;
 
+exports[`t-call (template calling t-call, global templates 1`] = `
+"function anonymous(context,extra
+) {
+    var h = this.h;
+    let c1 = [], p1 = {key:1};
+    var vn1 = h('div', p1, c1);
+    result = vn1;
+    let c2 = [], p2 = {key:2};
+    var vn2 = h('span', p2, c2);
+    c1.push(vn2);
+    c2.push({text: \`desk\`});
+    return vn1;
+}"
+`;
+
 exports[`t-call (template calling with unused body 1`] = `
 "function anonymous(context,extra
 ) {

tests/qweb/qweb.test.ts

@@ -662,6 +662,14 @@ describe("t-call (template calling", () => {
     const recursiveFn = Object.values(qweb.recursiveFns)[0];
     expect(recursiveFn.toString()).toMatchSnapshot();
   });
+
+  test("t-call, global templates", () => {
+    QWeb.registerTemplate('abcd', '<div><t t-call="john"/></div>')
+    qweb.addTemplate("john", `<span>desk</span>`);
+    const expected = "<div><span>desk</span></div>";
+    expect(trim(renderToString(qweb, "abcd"))).toBe(expected);
+  });
+
 });
 
 describe("foreach", () => {