Service Workers/Fetch: Fix Response constructor for empty/null

Source/modules/serviceworkers/Response.cpp

Index: Source/modules/serviceworkers/Response.cpp
diff --git a/Source/modules/serviceworkers/Response.cpp b/Source/modules/serviceworkers/Response.cpp
index 7ea930cab4e2ff520abb1839c0fd94d7b9709ba7..fc4ed03cb8520d1ea46a921c13d7917fb4daf259 100644
--- a/Source/modules/serviceworkers/Response.cpp
+++ b/Source/modules/serviceworkers/Response.cpp
@@ -59,8 +59,14 @@ FetchResponseData* createFetchResponseDataFromWebResponse(const WebServiceWorker
 
 }
 
+Response* Response::create(ExecutionContext* context, ExceptionState& exceptionState)
+{
+    return create(context, nullptr, ResponseInit(), exceptionState);
+}
+
 Response* Response::create(ExecutionContext* context, Blob* body, const Dictionary& responseInit, ExceptionState& exceptionState)
 {
+    ASSERT(body);
     return create(context, body, ResponseInit(responseInit, exceptionState), exceptionState);
 }