Improve error handling in state change failure response for better user feedback

templates/exam_overview_js.html

@@ -22,9 +22,22 @@
                 // show some message according to the response.
                 // For eg. A message box showing that the status has been changed
                 })
-                .fail(function (data) {
+                .fail(function (jqXHR) {
-                    console.log(data)
+                    console.log(jqXHR)
-                    toastr.error(`Failed to change state<br/>${data.responseJSON.status}`);
+                    var msg = 'Unknown error';
+                    try {
+                        if (jqXHR && jqXHR.responseJSON && jqXHR.responseJSON.status) {
+                            msg = jqXHR.responseJSON.status;
+                        } else if (jqXHR && jqXHR.responseText) {
+                            // fallback to raw responseText (may be HTML)
+                            msg = jqXHR.responseText;
+                        } else if (jqXHR && jqXHR.statusText) {
+                            msg = jqXHR.statusText;
+                        }
+                    } catch (e) {
+                        console.error('Error parsing failure response', e);
+                    }
+                    toastr.error(`Failed to change state<br/>${msg}`);
                 })
                 .always(function () {
                     console.log('[Done]');