Quota: Add null check

Source/modules/quota/StorageQuota.cpp

Index: Source/modules/quota/StorageQuota.cpp
diff --git a/Source/modules/quota/StorageQuota.cpp b/Source/modules/quota/StorageQuota.cpp
index 44226c7b28dabdc9795b61b160f64d07707076f3..5c07bf3b69608128d4021882382f31348230f496 100644
--- a/Source/modules/quota/StorageQuota.cpp
+++ b/Source/modules/quota/StorageQuota.cpp
@@ -106,7 +106,14 @@ ScriptPromise StorageQuota::requestPersistentQuota(ExecutionContext* executionCo
 {
     ASSERT(executionContext);
 
-    return StorageQuotaClient::from(executionContext)->requestPersistentQuota(executionContext, newQuota);
+    StorageQuotaClient* client = StorageQuotaClient::from(executionContext);
+    if (!client) {
+        RefPtr<ScriptPromiseResolver> resolver = ScriptPromiseResolver::create(executionContext);
+        resolver->reject(DOMError::create(NotSupportedError));
+        return resolver->promise();
+    }
+
+    return client->requestPersistentQuota(executionContext, newQuota);
 }
 
 StorageQuota::~StorageQuota()