Adding in an extra check, per the comments in 25b0ba9f9612583033b902a0e40345463a3a71d0.

diff --git a/src/ajax.js b/src/ajax.js
index 94426085e46d11e91c8d885bebd802c31258f26f..568a75dce1a8df9cec9a1b52a185599cac7a9daa 100644 (file)
--- a/src/ajax.js
+++ b/src/ajax.js
@@ -331,7 +331,7 @@ jQuery.extend({
                // Need an extra try/catch for cross domain requests in Firefox 3
                try {
                        // Set the correct header, if data is being sent
-                       if ( s.data || origSettings.contentType ) {
+                       if ( s.data || origSettings && origSettings.contentType ) {
                                xhr.setRequestHeader("Content-Type", s.contentType);
                        }