Merge branch '6.0' into 6.1

* 6.0:
  [HttpKernel] lock when writting profiles
  Using identical comparison for path validation
  [Mime] Fix email rendering when having inlined parts that are not related to the content
  fix typo
  [HttpFoundation] move flushing outside of Response::closeOutputBuffers
  [FrameworkBundle] Do not throw when describing a factory definition
  Fix checking result of DateTime::getLastErrors
  [WebProfilerBundle] Fix profile search bar link query params

VersionStrategy/StaticVersionStrategy.php

@@ -46,7 +46,7 @@ public function applyVersion(string $path): string
     {
         $versionized = sprintf($this->format, ltrim($path, '/'), $this->getVersion($path));
 
-        if ($path && '/' == $path[0]) {
+        if ($path && '/' === $path[0]) {
             return '/'.$versionized;
         }