fixing null checking for when there is no logo
diff --git a/src/main/org/freemarker/docgen/templates/header.ftl b/src/main/org/freemarker/docgen/templates/header.ftl
index bee1408..92b07e4 100644
--- a/src/main/org/freemarker/docgen/templates/header.ftl
+++ b/src/main/org/freemarker/docgen/templates/header.ftl
@@ -4,7 +4,7 @@
 <#import "google.ftl" as google>
 
 
-<#macro header logo>
+<#macro header>
   <div class="header-top-bg"><#t>
     <div class="site-width header-top"><#t>
       <#if logo??>
diff --git a/src/main/org/freemarker/docgen/templates/page.ftl b/src/main/org/freemarker/docgen/templates/page.ftl
index 48ab3a3..ed22543 100644
--- a/src/main/org/freemarker/docgen/templates/page.ftl
+++ b/src/main/org/freemarker/docgen/templates/page.ftl
@@ -52,7 +52,7 @@
   <!--[if lte IE 9]>
   <div style="background-color: #C00; color: #fff; padding: 12px 24px;">You need a modern browser to view this website.</div>
   <![endif]-->
-  <@header.header logo=logo />
+  <@header.header />
 
   <div class="site-width">