fix: Page.waitForDevicePrompt crash

Only call `deviceRequestPromptManager()` if the parent frame is not
null.

Bug: #11072
Follow-up-of: #9299

packages/puppeteer-core/src/cdp/Frame.ts

@@ -21,7 +21,6 @@ import {Frame, FrameEvent, throwIfDetached} from '../api/Frame.js';
 import type {HTTPResponse} from '../api/HTTPResponse.js';
 import type {Page, WaitTimeoutOptions} from '../api/Page.js';
 import {setPageContent} from '../common/util.js';
-import {assert} from '../util/assert.js';
 import {Deferred} from '../util/Deferred.js';
 import {disposeSymbol} from '../util/disposable.js';
 import {isErrorLike} from '../util/ErrorLike.js';
@@ -292,12 +291,12 @@ export class CdpFrame extends Frame {
   }
 
   #deviceRequestPromptManager(): DeviceRequestPromptManager {
-    if (this.isOOPFrame()) {
+    const parentFrame = this.parentFrame();
+    if (this.isOOPFrame() || parentFrame === null) {
       return this._frameManager._deviceRequestPromptManager(this.#client);
+    } else {
+      return parentFrame.#deviceRequestPromptManager();
     }
-    const parentFrame = this.parentFrame();
-    assert(parentFrame !== null);
-    return parentFrame.#deviceRequestPromptManager();
   }
 
   @throwIfDetached