[FIX] component: do not shadow the initial error in some cases

Before this commit, the error handling code simply destroyed the
application whenever an unhandled error occured in the owl rendering
process. This is perfectly fine, except that since the application is
potentially corrupted, the destroy code may crash as well. We simply
catch those errors to avoid shadowing the main issue.

closes #866

tests/component/error_handling.test.ts

@@ -586,4 +586,25 @@ describe("component error handling (catchError)", () => {
     await mount(Parent, { target: fixture });
     expect(fixture.innerHTML).toBe("<div>Error</div>");
   });
+
+  test("errors in mounted and in willUnmount", async () => {
+    expect.assertions(1);
+    class Example extends Component {
+      static template = xml`<div/>`;
+      val;
+      mounted() {
+        throw new Error("Error in mounted");
+        this.val = { foo: "bar" };
+      }
+      willUnmount() {
+        console.log(this.val.foo);
+      }
+    }
+
+    try {
+      await mount(Example, { target: fixture });
+    } catch (e) {
+      expect(e.message).toBe("Error in mounted");
+    }
+  });
 });