Twigのエラーが発生しておりまして、困っております。

注文確認画面から決済手続きボタンを押すと、システムエラーが発生します。
（shopping/confirm　へ値を投げるボタン）

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Twig_Error_Loader in Chain.php line 115:
Template "" is not defined.
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なにもテンプレートを選択していない状態で、
なぜかテンプレート読み込み処理に進んでしまっているのだと思うのですが、EC-Cube3が触りたてのため、なにが起こっているか全くわからず困っています。

ご助力頂ければと思います。

=============================
in Chain.php line 115
at Twig_Loader_Chain->getCacheKey(null) in Environment.php line 312
at Twig_Environment->getTemplateClass(null, null) in Environment.php line 378
at Twig_Environment->loadTemplate(null) in Environment.php line 347
at Twig_Environment->render(null, array('header' => 'この度はご注文い.....
.....━', 'Order' => object(Order))) in ApplicationTrait.php line 273
at ApplicationTrait->renderView(null, array('header' => 'この度はご注文いただき....
━', 'Order' => object(Order))) in MailService.php line 225
at MailService->sendOrderMail(object(Order)) in ShoppingService.php line 1221
at ShoppingService->sendOrderMail(object(Order)) in ShoppingController.php line 248
at ShoppingController->confirm(object(Application), object(Request))
at call_user_func_array(array(object(ShoppingController), 'confirm'), array(object(Application), object(Request))) in HttpKernel.php line 144
at HttpKernel->handleRaw(object(Request), '1') in HttpKernel.php line 64
at HttpKernel->handle(object(Request), '1', true) in Application.php line 586
at Application->handle(object(Request)) in Application.php line 563
at Application->run() in index_dev.php line 104

=============================
WARNING - skip OrderStatusColor loading. service provider class not foud.
Context: {"class":"\\Plugin\\OrderStatusColor\\ServiceProvider\\ServiceProvider"}
INFO - Matched route "shopping_confirm".
Context: {"route_parameters":{"_controller":"\\Eccube\\Controller\\ShoppingController::confirm","_route":"shopping_confirm"},"request_uri":"https://grmet-navi-info.ssl-xserver.jp/index_dev.php/shopping/confirm"}
INFO - > POST /index_dev.php/shopping/confirm
CRITICAL - Twig_Error_Loader: Template "" is not defined. (uncaught exception) at /home/sasukedesign/grmet-navi.info/public_html/eccube3/vendor/twig/twig/lib/Twig/Loader/Chain.php line 115
Context: {"exception":"Object(Twig_Error_Loader)"}