Merge branch '4.4'

* 4.4:
  [Mailer] Fix SmtpEnvelope renaming to Envelope
  fixed "link" to Contracts packages
  [WebProfilerBundle] Fix time panel legend buttons
  Some styling tweaks
  Fixed cache pools affecting each other due to an overwritten seed variable
  don't change state in case of exception
  properly catch legacy tag syntax usages
  minor tweaks to the welcome page

Author: xabbuh

ValidatorBuilder.php

@@ -263,12 +263,12 @@ public function setMetadataFactory(MetadataFactoryInterface $metadataFactory)
      */
     public function setMappingCache(CacheItemPoolInterface $cache)
     {
-        $this->mappingCache = $cache;
-
         if (null !== $this->metadataFactory) {
             throw new ValidatorException('You cannot set a custom mapping cache after setting a custom metadata factory. Configure your metadata factory instead.');
         }
 
+        $this->mappingCache = $cache;
+
         return $this;
     }