[Mime] use isRendered method to avoid rendering an email twice

Author: walva

src/Symfony/Bridge/Twig/Mime/BodyRenderer.php

@@ -45,7 +45,7 @@ public function render(Message $message): void
             return;
         }
 
-        if (null === $message->getTextTemplate() && null === $message->getHtmlTemplate()) {
+        if ($message->isRendered()) {
             // email has already been rendered
             return;
         }

src/Symfony/Bridge/Twig/Tests/Mime/BodyRendererTest.php

@@ -105,10 +105,14 @@ public function testRenderedOnce()
         ;
         $email->textTemplate('text');
 
+        $this->assertFalse($email->isRendered());
         $renderer->render($email);
+        $this->assertTrue($email->isRendered());
+
         $this->assertEquals('Text', $email->getTextBody());
 
         $email->text('reset');
+        $this->assertTrue($email->isRendered());
 
         $renderer->render($email);
         $this->assertEquals('reset', $email->getTextBody());