fix browser title for title-less posts

_layouts/default.html

@@ -6,7 +6,7 @@
     <meta http-equiv="X-UA-Compatible" content="IE=edge">
     <meta name="viewport" content="width=device-width, initial-scale=1">
     
-    <title>{{ site.title }}{% if page.title %} &mdash; {{ page.title }}{% endif %}</title>
+    <title>{{ site.title }}{% if page.title and page.title != "" %} &mdash; {{ page.title }}{% endif %}</title>
 
     <link rel="stylesheet" href="{{ '/assets/css/main.css' | absolute_url }}?{{ site.time | date: '%s%N' }}">