fix: unable to find instance in case of ng17 control flow

ViewContainerRef actually returns the wrong length in case of
Angular 17 Control Flow. By checking that the returned value is
not null we should be safe.

Solves #7216

libs/ng-mocks/src/lib/mock-helper/crawl/el-def-get-parent.ts

@@ -24,6 +24,10 @@ const getScanViewRefRootNodes = (node: any, child: any): Array<[number, any]> =>
   const result: Array<[number, any]> = [];
   for (let vrIndex = 0; vrIndex < vcr.length; vrIndex += 1) {
     const vr = vcr.get(vrIndex);
+    if (!vr) {
+      continue;
+    }
+
     for (let rnIndex = 0; rnIndex < (vr as any).rootNodes.length; rnIndex += 1) {
       result.push([rnIndex, (vr as any).rootNodes[rnIndex]]);
     }

tests/issue-7216/test.spec.ts

@@ -0,0 +1,47 @@
+import { CommonModule } from '@angular/common';
+import { Component, NgModule, VERSION } from '@angular/core';
+
+import { MockBuilder, MockRender, ngMocks } from 'ng-mocks';
+
+// @see https://github.com/help-me-mom/ng-mocks/issues/7216
+describe('issue-7216', () => {
+  if (Number.parseInt(VERSION.major, 10) < 17) {
+    it('needs a17+', () => {
+      expect(true).toBeTruthy();
+    });
+
+    return;
+  }
+
+  @Component({
+    selector: 'target',
+    template: `
+      @if (hasChild) {
+        <child></child>
+      }
+    `,
+  })
+  class TargetComponent {
+    public readonly hasChild = true;
+  }
+
+  @Component({
+    selector: 'child',
+    template: '',
+  })
+  class ChildComponent {}
+
+  @NgModule({
+    imports: [CommonModule],
+    declarations: [TargetComponent, ChildComponent],
+  })
+  class TargetModule {}
+
+  beforeEach(() => MockBuilder(TargetComponent, TargetModule));
+
+  it('finds child-element', () => {
+    MockRender(TargetComponent);
+
+    expect(ngMocks.findInstance(ChildComponent)).toBeTruthy();
+  });
+});