Hello,

Some older versions of Mediawiki (1.16) do not provide "mediatype" in "iiprop" for media. Then its worker crashes when it tries to parse a reply from a server.

Here is workaround for an issue:

--- ext.core.LinkHandler.js-    2015-04-22 15:30:04.000000000 +0300
+++ ext.core.LinkHandler.js    2015-04-22 17:03:11.000000000 +0300
@@ -1011,7 +1012,11 @@
         // Add (read-only) information about original file size (T64881)
         img.addAttribute( 'data-file-width', info.width );
         img.addAttribute( 'data-file-height', info.height );
-        img.addAttribute( 'data-file-type', info.mediatype.toLowerCase() );
+        if (info.mediatype) {
+            img.addAttribute( 'data-file-type', info.mediatype.toLowerCase() );
+        }
     }
 
     if ( hasImageLink ) {