修复Firefox下上传图片返回json数据为undefined的问题

plugins/image-dialog/image-dialog.js

@@ -150,7 +150,12 @@
 							uploadIframe.onload = function() {
                                 loading(false);
 
-								var json = uploadIframe.contentWindow.document.body.innerText;
+								var json = "";
+								if (uploadIframe.contentWindow) {
+									json = uploadIframe.contentWindow.document.body ? uploadIframe.contentWindow.document.body.innerHTML : null;
+								} else if (uploadIframe.contentDocument) {
+									json = uploadIframe.contentDocument.document.body ? uploadIframe.contentDocument.document.body.innerHTML : null;
+								}
 								json = (typeof JSON.parse !== "undefined") ? JSON.parse(json) : eval("(" + json + ")");
 
 								if (json.success === 1)