Exit early if ToScriptStateForMainWorld() is nullptr in NavigationApi…

…::DispatchNavigateEvent

(cherry picked from commit ac216c5)

Bug: 1316437
Change-Id: Id3e2f141541cae259ce38f0836f659fdcb742973
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3587615
Reviewed-by: Domenic Denicola <domenic@chromium.org>
Commit-Queue: Domenic Denicola <domenic@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#993339}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3594452
Auto-Submit: Nate Chapin <japhet@chromium.org>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/branch-heads/5005@{#38}
Cr-Branched-From: 5b4d945-refs/heads/main@{#992738}

third_party/blink/renderer/core/navigation_api/navigation_api.cc

@@ -751,6 +751,8 @@ NavigationApi::DispatchResult NavigationApi::DispatchNavigateEvent(
 
   auto* script_state =
       ToScriptStateForMainWorld(GetSupplementable()->GetFrame());
+  if (!script_state)
+    return DispatchResult::kContinue;
   ScriptState::Scope scope(script_state);
 
   if (params.frame_load_type == WebFrameLoadType::kBackForward &&