Merge branch '6.4' into 7.1

* 6.4:
  [FrameworkBundle] Add missing `not-compromised-password` entry in XSD
  [AssetMapper] Fix CssCompiler matches url in comments
  Add support for doctrine/persistence 4
  Ensure TransportExceptionInterface populates stream debug data
  Fix typo in validators.sk.xlf
  [Mime] Fix body validity check in `Email` when using `Message::setBody()`
  Review Arabic translations for the validator
  Fixed mistakes in proper hebrew writing in the previous translation and confirmed the rest to be correct and in the same style.
  Review translation
  [Cache] Don't clear system caches on cache:clear
  [FrameworkBundle] Fix patching refs to the tmp warmup dir in files generated by optional cache warmers
  Mark Czech Validator translation as reviewed
  [PropertyInfo] Fix `TypeTest` duplicated assert
  [HtmlSanitizer] Avoid accessing non existent array key when checking for hosts validity
  Update validators.ar.xlf
  [DomCrawler] Make `ChoiceFormField::isDisabled` return `true` for unchecked disabled checkboxes

Author: xabbuh

Transport/Smtp/SmtpTransport.php

@@ -205,11 +205,11 @@ protected function doSend(SentMessage $message): void
             $this->ping();
         }
 
-        if (!$this->started) {
-            $this->start();
-        }
-
         try {
+            if (!$this->started) {
+                $this->start();
+            }
+
             $envelope = $message->getEnvelope();
             $this->doMailFromCommand($envelope->getSender()->getEncodedAddress());
             foreach ($envelope->getRecipients() as $recipient) {