Fix coffeescript issue on Linux

On Linux, coffeescript refuses to compile unless the `catch` keyword has an error
variable to bind to. On Mac, it works just fine either way. Go figure.

cms/static/coffee/src/main.coffee

@@ -21,7 +21,7 @@ $ ->
     if jqXHR.responseText
       try
         message = JSON.parse(jqXHR.responseText).error
-      catch
+      catch error
         message = _.str.truncate(jqXHR.responseText, 300)
     else
       message = gettext("This may be happening because of an error with our server or your internet connection. Try refreshing the page or making sure you are online.")