add test and retained fix

packages/webview_flutter/webview_flutter_wkwebview/darwin/Tests/FrameInfoProxyAPITests.swift

@@ -28,6 +28,16 @@ class FrameInfoProxyAPITests: XCTestCase {
 
     XCTAssertEqual(value?.value, instance!.request)
   }
+
+  @MainActor func testNilRequest() {
+    let registrar = TestProxyApiRegistrar()
+    let api = registrar.apiDelegate.pigeonApiWKFrameInfo(registrar)
+
+    let instance = TestFrameInfoWithNilRequest()
+    let value = try? api.pigeonDelegate.request(pigeonApi: api, pigeonInstance: instance)
+
+    XCTAssertNil(value)
+  }
 }
 
 class TestFrameInfo: WKFrameInfo {
@@ -39,3 +49,9 @@ class TestFrameInfo: WKFrameInfo {
     return URLRequest(url: URL(string: "https://google.com")!)
   }
 }
+
+class TestFrameInfoWithNilRequest: WKFrameInfo {
+  override var isMainFrame: Bool {
+    return true
+  }
+}

packages/webview_flutter/webview_flutter_wkwebview/darwin/webview_flutter_wkwebview/Sources/webview_flutter_wkwebview/FrameInfoProxyAPIDelegate.swift

@@ -11,7 +11,8 @@ extension WKFrameInfo {
   //
   // See https://github.com/flutter/flutter/issues/163549 and https://developer.apple.com/forums/thread/77888.
   var maybeRequest: URLRequest? {
-    return self.perform(#selector(getter: WKFrameInfo.request))?.takeUnretainedValue() as! URLRequest?
+    return self.perform(#selector(getter: WKFrameInfo.request))?.takeUnretainedValue()
+      as! URLRequest?
   }
 }