Fix vardumper php-debugbar#474 (php-debugbar#475)

Author: barryvdh

src/DebugBar/DataFormatter/DebugBarVarDumper.php

@@ -285,7 +285,7 @@ public function renderVar($data)
      */
     public function getAssets() {
         $dumper = $this->getDumper();
-        $dumper->setDumpHeader(null); // this will cause the default dump header to regenerate
+        $dumper->resetDumpHeader(); // this will cause the default dump header to regenerate
         return array(
             'inline_head' => array(
                 'html_var_dumper' => $dumper->getDumpHeaderByDebugBar(),

src/DebugBar/DataFormatter/VarDumper/DebugBarHtmlDumper.php

@@ -10,6 +10,14 @@
  */
 class DebugBarHtmlDumper extends HtmlDumper
 {
+    /**
+     * Resets an HTML header.
+     */
+    public function resetDumpHeader()
+    {
+        $this->dumpHeader = null;
+    }
+
     public function getDumpHeaderByDebugBar() {
         // getDumpHeader is protected:
         return str_replace('pre.sf-dump', '.phpdebugbar pre.sf-dump', $this->getDumpHeader());