Merge branch '5.4' into 6.0

* 5.4:
  [String] Add tests for AsciiSlugger
  [Serializer] Fix get accessor regex in AnnotationLoader
  [HttpKernel] Fix passing `null` to `\trim()` method in LoggerDataCollector
  [Translation] Crowdin provider throw Exception when status is 50x
  Always attempt to listen for notifications
  add missing changelog entry for the AtLeastOneOf constraint
  validate nested constraints only if they are in the same group

Author: fabpot

DataCollector/LoggerDataCollector.php

@@ -144,7 +144,7 @@ public function getFilters()
 
         $allChannels = [];
         foreach ($this->getProcessedLogs() as $log) {
-            if ('' === trim($log['channel'])) {
+            if ('' === trim($log['channel'] ?? '')) {
                 continue;
             }