Fixed problem with handling web_url

Fixed a problem with handling web_url variable if not defined in skin.conf

index.html.tmpl

@@ -23,8 +23,8 @@
     <meta property="og:site_name" content="$station.location Weather Station" />
     <meta property="og:title" content="$station.location Current Weather Conditions"/>
     #end if
-    <meta property="og:image" content="$Extras.web_url/daytempdew.png"/>
     #if $Extras.has_key('web_url')
+    <meta property="og:image" content="$Extras.web_url/daytempdew.png"/>
     <meta property="og:url" content="$Extras.web_url"/>
     #end if
     #if $Extras.has_key('cwop')