fix(core): do not crash for signal query that does not have any match…

…es (#54353)

The newly introduced signal queries would error if no match exists, due to an
invalid read within the query internals.

This commit addresses the crash by allowing there to be no matches.

PR Close #54353

packages/core/src/render3/query.ts

@@ -354,9 +354,9 @@ function materializeViewResults<T>(
   const lQuery = lView[QUERIES]!.queries![queryIndex];
   if (lQuery.matches === null) {
     const tViewData = tView.data;
-    const tQueryMatches = tQuery.matches!;
-    const result: T|null[] = [];
-    for (let i = 0; i < tQueryMatches.length; i += 2) {
+    const tQueryMatches = tQuery.matches;
+    const result: Array<T|null> = [];
+    for (let i = 0; tQueryMatches !== null && i < tQueryMatches.length; i += 2) {
       const matchedNodeIdx = tQueryMatches[i];
       if (matchedNodeIdx < 0) {
         // we at the <ng-template> marker which might have results in views created based on this

packages/core/test/acceptance/authoring/signal_queries_spec.ts

@@ -183,6 +183,23 @@ describe('queries as signals', () => {
          expect(result2.length).toBe(1);
          expect(result2).toBe(result1);
        });
+
+    it('should be empty when no query matches exist', () => {
+      @Component({
+        standalone: true,
+        template: ``,
+      })
+      class AppComponent {
+        result = viewChild('unknown');
+        results = viewChildren('unknown');
+      }
+
+      const fixture = TestBed.createComponent(AppComponent);
+      fixture.detectChanges();
+
+      expect(fixture.componentInstance.result()).toBeUndefined();
+      expect(fixture.componentInstance.results().length).toBe(0);
+    });
   });
 
   describe('content queries', () => {
@@ -319,5 +336,32 @@ describe('queries as signals', () => {
 
       expect(queryDir.results().length).toBe(2);
     });
+
+    it('should be empty when no query matches exist', () => {
+      @Directive({
+        selector: '[declare]',
+        standalone: true,
+      })
+      class DeclareQuery {
+        result = contentChild('unknown');
+        results = contentChildren('unknown');
+      }
+
+      @Component({
+        standalone: true,
+        imports: [DeclareQuery],
+        template: `<div declare></div>`,
+      })
+      class AppComponent {
+      }
+
+      const fixture = TestBed.createComponent(AppComponent);
+      fixture.detectChanges();
+      const queryDir =
+          fixture.debugElement.query(By.directive(DeclareQuery)).injector.get(DeclareQuery);
+
+      expect(queryDir.result()).toBeUndefined();
+      expect(queryDir.results().length).toBe(0);
+    });
   });
 });