[REF] component: make observer and state optional

tests/component.test.ts

@@ -72,7 +72,7 @@ describe("basic widget properties", () => {
   test("props and state are properly defined", async () => {
     const widget = new Widget(env);
     expect(widget.props).toEqual({});
-    expect(widget.state).toEqual({});
+    expect(widget.state).toEqual(undefined);
   });
 
   test("has no el after creation", async () => {