Protecting against other possible uses of invalid V8 execution context.

Source/modules/indexeddb/IDBTransaction.cpp

Index: Source/modules/indexeddb/IDBTransaction.cpp
diff --git a/Source/modules/indexeddb/IDBTransaction.cpp b/Source/modules/indexeddb/IDBTransaction.cpp
index 35d7012ad26e1dae06b228e50176e0117f6af0b9..19301176e90ae79ad9c63fda5be9c8f86dfaefd8 100644
--- a/Source/modules/indexeddb/IDBTransaction.cpp
+++ b/Source/modules/indexeddb/IDBTransaction.cpp
@@ -341,6 +341,10 @@ ExecutionContext* IDBTransaction::executionContext() const
 bool IDBTransaction::dispatchEvent(PassRefPtr<Event> event)
 {
     IDB_TRACE("IDBTransaction::dispatchEvent");
+    if (m_contextStopped || !executionContext()) {
+        m_state = Finished;
+        return false;
+    }
     ASSERT(m_state != Finished);
     ASSERT(m_hasPendingActivity);
     ASSERT(executionContext());