## Steps to replicate the issue
A recent uptick in client errors was caused by the following stack trace:
https://logstash.wikimedia.org/goto/edadec34a9c464c8faa71411bf2287c5
```
at initMediaViewer https://es.m.wikipedia.org/w/load.php?lang=es&modules=skins.minerva.scripts&skin=minerva&version=15hi7:7:317
at eval https://es.m.wikipedia.org/w/load.php?lang=es&modules=skins.minerva.scripts&skin=minerva&version=15hi7:12:62
at Object.fire https://es.m.wikipedia.org/w/load.php?lang=es&modules=mediawiki.base&skin=minerva&version=1hazk:4:699
at Object.<anonymous> https://www.mediawiki.org/w/index.php?title=XTools/ArticleInfo.js&action=raw&ctype=text/javascript:39:37
at fire https://es.m.wikipedia.org/w/load.php?lang=es&modules=jquery%2Cvue%7Cmobile.startup&skin=minerva&version=1y6cb:42:705
at Object.fireWith [as resolveWith] https://es.m.wikipedia.org/w/load.php?lang=es&modules=jquery%2Cvue%7Cmobile.startup&skin=minerva&version=1y6cb:43:903
at done https://es.m.wikipedia.org/w/load.php?lang=es&modules=jquery%2Cvue%7Cmobile.startup&skin=minerva&version=1y6cb:127:417
at XMLHttpRequest.<anonymous> https://es.m.wikipedia.org/w/load.php?lang=es&modules=jquery%2Cvue%7Cmobile.startup&skin=minerva&version=1y6cb:131:59
```
{F43051477, size=full}
### What happens?
While the root cause of this error is unknown, the error throws because `$container[ 0 ]` on the following lines in Minerva is undefined, which means the content container is empty.
```lang=js, name=MinervaNeue/resources/skins.minerva.scripts/initMobile.js
mw.hook( 'wikipage.content' ).add( function ( $container ) {
// If the MMV module is missing or disabled from the page, initialise our version
if ( desktopMMV === null || desktopMMV === 'registered' ) {
initMediaViewer( $container[ 0 ] );
}
```
## What should have happened instead?
`mw.hook( 'wikipage.content' ).fire` is fired [[ https://codesearch.wmcloud.org/search/?q=%5C%28+%27wikipage.content%27+%5C%29.fire&files=&excludeFiles=&repos= | often enough ]] that we can't guarantee it will return a DOM node.
**We should validate that `$container` exists before calling `initMediaViewer()`**
## QA Requirements
The mobile site should not throw an error when a gadget uses the `wikipage.content` hook.
To simulate this situation, the following line can be executed in the browser console:
```lang=js
mw.hook( 'wikipage.content' ).fire( $( '#does-not-exist' ) );
```
The output of that line should not produce an error.