[FIX] t-call-context: fix capture making component available in ctx

Previously, when using a component with a slot within a t-call with
t-call-context, the component would become available again inside the
slot despite the t-call-context. This was caused by the fact that the
capture helper function creates an object with the component as its
prototype which is incorrect. It should just use the previous context as
its prototype.

tests/components/t_call.test.ts

@@ -316,7 +316,7 @@ describe("t-call", () => {
     expect(fixture.innerHTML).toBe("childaaronchildlucas");
   });
 
-  test.only("t-call-context: ComponentNode is not looked up in the context", async () => {
+  test("t-call-context: ComponentNode is not looked up in the context", async () => {
     let child: any;
     class Child extends Component {
       static template = xml`<t t-slot="default"/>`;
@@ -357,4 +357,30 @@ describe("t-call", () => {
     expect(Object.keys(child.__owl__.refs)).toEqual([]);
     expect(Object.keys(root.__owl__.refs)).toEqual(["myRef", "myRef2"]);
   });
+
+  test("t-call-context: slots don't make component available again when context is captured", async () => {
+    class Child extends Component {
+      static template = xml`<t t-slot="default"/>`;
+    }
+
+    class Root extends Component {
+      static template = xml`<t t-call="template" t-call-context="{}"/>`;
+      static components = { Child };
+      someValue = "Hello";
+    }
+
+    await mount(Root, fixture, {
+      test: true,
+      templates: `
+        <templates>
+          <t t-name="template">
+            <t t-set="dummy" t-value="0"/>
+            <Child>
+              <t t-esc="someValue"/>
+            </Child>
+          </t>
+        </templates>`,
+    });
+    expect(fixture.innerHTML).toBe("");
+  });
 });