Merge branch '4.1'

* 4.1: (23 commits)
  [Routing] fix trailing slash redirection when using RedirectableUrlMatcher
  [PropertyAccessor] fix encoding of cache keys
  [WebProfiler] Detect empty file paths in file viewer
  fixed CS
  Changes for upcoming Travis' infra migration
  Doc fix: clarify isMethodCacheable() returns true only for GET & HEAD
  [MonologBridge] Return empty list for unknonwn requests
  [DomCrawler] exclude fields inside "template" tags
  Use XLIFF source rather than resname when there's no target
  [DoctrineBridge] catch errors while converting to db values in data collector
  [DoctrineBridge] fix case sensitivity issue in RememberMe\DoctrineTokenProvider
  [EventDispatcher] Unwrap wrapped listeners internally
  [Routing] fix trailing slash redirection when using RedirectableUrlMatcher
  Removed the return type phpdoc
  fix authorization checker variable name
  [Routing] Remove duplicate schemes and methods for invokable controllers
  Indentation error
  [HttpFoundation] Fix trailing space for mime-type with parameters
  [HttpFoundation] Fixed absolute Request URI with default port
  [Bridge/PhpUnit] fix the fix
  ...

Author: nicolas-grekas

Extension/CodeExtension.php

@@ -135,7 +135,7 @@ public function formatArgsAsText($args)
      */
     public function fileExcerpt($file, $line, $srcContext = 3)
     {
-        if (is_readable($file)) {
+        if (is_file($file) && is_readable($file)) {
             // highlight_file could throw warnings
             // see https://bugs.php.net/bug.php?id=25725
             $code = @highlight_file($file, true);
@@ -158,6 +158,8 @@ public function fileExcerpt($file, $line, $srcContext = 3)
 
             return '<ol start="'.max($line - $srcContext, 1).'">'.implode("\n", $lines).'</ol>';
         }
+
+        return null;
     }
 
     /**