Fix a bug with FRPtools when a container property is set to a falsey value

package.json

@@ -1,6 +1,6 @@
 {
 	"name": "frptools",
-	"version": "3.2.1",
+	"version": "3.2.2",
 	"description": "Observable Property and Computed data streams",
 	"main": "src/index.js",
 	"files": [

spec/container.spec.js

@@ -2,6 +2,17 @@ import { container, computed } from '../src/index.js';
 import { dirtyMock, hashSet } from '../src/testUtil.js';
 
 describe('A container', () => {
+	it('tracks properties', () => {
+		let i = 0;
+		const a = container({}, () => i++);
+
+		a.a = 1;
+		expect(a.a).toBe(a._.a);
+
+		a.b = false;
+		expect(a.b).toBe(a._.b);
+	});
+
 	it('notifies dependents of updates', () => {
 		let runCount = 0;
 		let currentValue = new Set();

src/container.js

@@ -48,7 +48,9 @@ export function container(store, hash) {
 			target[name] = newVal;
 			checkUpdate(target);
 
-			return newVal;
+			// Returning a falsey value causes TypeError
+			// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/handler/set#Invariants
+			return newVal || true;
 		}
 	});