Bug Fix for Inserting Images

I noticed when using Firefox 65 that trying to insert an image would cause the Browse tab to show the loading spinner indefinitely.  I found the bug and fixed it.

• Open skins\common\yui\mindtouch\link_navigator.js
• Search for "Content-Type" so you find this section:
  
  

  var contentType = o.getResponseHeader['Content-Type'] ?
                    o.getResponseHeader['Content-Type'] :
                    o.getResponseHeader['Content-type']; 

• Change it to this:
  
  

  var contentType = o.getResponseHeader['Content-Type'] ||
                    o.getResponseHeader['Content-type'] ||
                    o.getResponseHeader['content-type'];  
  

It's searching for the "Content-Type" or "Content-type" header, but Firefox 65 uses "content-type".  Now it checks all three.