fix(data): allow 0 to be a valid key (#3830)

Closes #3828

Author: timdeschryver

modules/data/spec/actions/entity-action-guard.spec.ts

@@ -114,6 +114,11 @@ describe('EntityActionGuard', () => {
       action = createAction(1);
       expect(guard.mustBeKey(action)).toBe(1);
     });
+
+    it('should not throw if key is 0', () => {
+      action = createAction(0);
+      expect(guard.mustBeKey(action)).toBe(0);
+    });
   });
 
   describe('mustBeKeys', () => {

modules/data/src/actions/entity-action-guard.ts

@@ -43,7 +43,7 @@ export class EntityActionGuard<T> {
   /** Throw if the action payload is not a single, valid key */
   mustBeKey(action: EntityAction<string | number>): string | number | never {
     const data = this.extractData(action);
-    if (!data) {
+    if (data === undefined) {
       throw new Error(`should be a single entity key`);
     }
     if (this.isNotKeyType(data)) {