Issue #1371852 by BarisW: Fixed Patch to logo in preview.html misses core subfolder.

core/themes/bartik/color/preview.html

 <div id="preview">
 
   <div id="preview-header">
-    <div id="preview-logo"><img src="../../../themes/bartik/logo.png" alt="Site Logo" /></div>
+    <div id="preview-logo"><img src="../../../core/themes/bartik/logo.png" alt="Site Logo" /></div>
     <div id="preview-site-name">Bartik</div>
     <div id="preview-main-menu">
       <ul id="preview-main-menu-links">