**Screencast**: {F2525157}
**Description**: I'm getting an empty error message like this two or more times a day since the last week:
```lang=json
{
"errorMessage": ": ",
"url": "https://gl.wikipedia.org/static/1.26wmf20/extensions/CentralNotice/modules/ext.centralNotice.bannerController/bannerController.js",
"lineNumber": 339,
"columnNumber": 0,
"errorObject": {}
}
```
I got the info above when I accessed
https://gl.wikipedia.org/wiki/Usuario:Elisardojm/monobook.js?diff=0
for the first time (the error didn't happen after a page reload), in debug mode.
By clicking on the console, I could see that the problematic line was this:
> navigator.sendBeacon( url.toString() );
When in production mode, the error is similar, but the URL we get doesn't make it clear that the error comes from centralNotice. E.g.: this was the message I got at
https://pt.wikipedia.org/w/index.php?diff=next&oldid=43209909
```lang=json
{
"errorMessage": ": ",
"url": "https://pt.wikipedia.org/w/load.php?debug=false&lang=pt&modules=ext.centralNotice.bannerChoiceData%2CbannerController%7Cext.centralNotice.bannerController.lib%7Cext.centralauth.centralautologin.clearcookie%7Cext.uls.init%2Cinterface%2Cpreferences%2Cwebfonts%7Cext.visualEditor.desktopArticleTarget.init%7Cext.visualEditor.track%2Cve%7Cjquery.byteLength%2Ccookie%2CtabIndex%2Cthrottle-debounce%2Ctipsy%7Cmediawiki.Title%2CUri%2Capi%2Ccldr%2Ccookie%2CjqueryMsg%2Clanguage%2Cuser%7Cmediawiki.language.data%2Cinit%7Cmediawiki.libs.pluralruleparser%7Cmediawiki.page.startup%7Cskins.vector.js%7Cuser.defaults&skin=vector&version=71829dff924d&*",
"lineNumber": 6,
"columnNumber": 0,
"errorObject": {}
}
```
Usually, the error didn't happen again after a page reload but in the most recent occurrences, it was happening consistently on every page load, both in production and in debug mode.
**Browser information**
> `navigator.userAgent` > Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Firefox/38.0 Iceweasel/38.2.0