Fix crash in background merging of deserialized scripts

BackgroundMergeTask::CompleteMergeInForeground contained an incorrect
assumption that some SharedFunctionInfos would have bytecode arrays.

Bug: v8:12808, chromium:1360024
Change-Id: I42ca22fc3a4412aea5e5a433e63c685eaf2af242
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3888198Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
Cr-Commit-Position: refs/heads/main@{#83133}

src/codegen/compiler.cc

@@ -2099,11 +2099,15 @@ Handle<SharedFunctionInfo> BackgroundMergeTask::CompleteMergeInForeground(
   // pools is required.
   if (forwarder.HasAnythingToForward()) {
     for (Handle<SharedFunctionInfo> new_sfi : used_new_sfis_) {
-      forwarder.AddBytecodeArray(new_sfi->GetBytecodeArray(isolate));
+      if (new_sfi->HasBytecodeArray(isolate)) {
+        forwarder.AddBytecodeArray(new_sfi->GetBytecodeArray(isolate));
+      }
     }
     for (const auto& new_compiled_data : new_compiled_data_for_cached_sfis_) {
-      forwarder.AddBytecodeArray(
-          new_compiled_data.cached_sfi->GetBytecodeArray(isolate));
+      if (new_compiled_data.cached_sfi->HasBytecodeArray(isolate)) {
+        forwarder.AddBytecodeArray(
+            new_compiled_data.cached_sfi->GetBytecodeArray(isolate));
+      }
     }
     forwarder.IterateAndForwardPointers();
   }

test/unittests/api/deserialize-unittest.cc

@@ -617,4 +617,19 @@ TEST_F(MergeDeserializedCodeTest, MainThreadReMerge) {
                      true);                  // lazy_should_be_compiled
 }
 
+TEST_F(MergeDeserializedCodeTest, Regress1360024) {
+  // This test case triggers a re-merge on the main thread, similar to
+  // MainThreadReMerge. However, it does not retain the lazy function's SFI at
+  // any step, which causes the merge to use the SFI from the newly deserialized
+  // script for that function. This exercises a bug in the original
+  // implementation where the re-merging on the main thread would crash if the
+  // merge algorithm had selected any uncompiled SFIs from the new script.
+  TestOffThreadMerge(kToplevelAndEager,      // retained_before_background_merge
+                     kToplevelAndEager,      // aged_before_background_merge
+                     true,                   // run_code_after_background_merge
+                     kToplevelAndEager,      // retained_after_background_merge
+                     kToplevelSfiFlag,       // aged_after_background_merge
+                     true);                  // lazy_should_be_compiled
+}
+
 }  // namespace v8