IDL: make optional arguments (without default) explicit sometimes

Source/modules/indexeddb/IDBCursor.cpp

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 134 matching lines @@
     }
 
     m_request->setPendingCursor(this);
     m_gotValue = false;
     m_backend->advance(count, WebIDBCallbacksImpl::create(m_request).leakPtr());
 }
 
 void IDBCursor::continueFunction(ScriptState* scriptState, const ScriptValue& keyValue, ExceptionState& exceptionState)
 {
     IDB_TRACE("IDBCursor::continue");
-    IDBKey* key = keyValue.isUndefined() || keyValue.isNull() ? nullptr : scriptValueToIDBKey(scriptState->isolate(), keyValue);
+    IDBKey* key = keyValue.isEmpty() || keyValue.isUndefined() || keyValue.isNull() ? nullptr : scriptValueToIDBKey(scriptState->isolate(), keyValue);
     if (key && !key->isValid()) {
         exceptionState.throwDOMException(DataError, IDBDatabase::notValidKeyErrorMessage);
         return;
     }
     continueFunction(key, 0, exceptionState);
 }
 
 void IDBCursor::continuePrimaryKey(ScriptState* scriptState, const ScriptValue& keyValue, const ScriptValue& primaryKeyValue, ExceptionState& exceptionState)
 {
     IDB_TRACE("IDBCursor::continuePrimaryKey");
@@ skipping 221 matching lines @@
     case WebIDBCursorDirectionPrevNoDuplicate:
         return IndexedDBNames::prevunique;
 
     default:
         ASSERT_NOT_REACHED();
         return IndexedDBNames::next;
     }
 }
 
 } // namespace blink