Chrome and Opera browsers show a Javascript runtime error while creating a <mapframe> map. The map creation is stopped, it is not dynamical (i.e. the map is "freezed"). This bug is accidental but frequent.
The error log:
```
Exception in module-execute in module ext.kartographer.settings:
load.php?debug=false&lang=de&modules=jquery%2Cmediawiki|mediawiki.legacy.wikibits&only=scripts&skin=vector&version=18kdz1s:175 TypeError: Cannot read property '4' of null
at <anonymous>:19:342
at <anonymous>:19:525
at runScript (load.php?debug=false&lang=de&modules=jquery%2Cmediawiki|mediawiki.legacy.wikibits&only=scripts&skin=vector&version=18kdz1s:160)
at checkCssHandles (load.php?debug=false&lang=de&modules=jquery%2Cmediawiki|mediawiki.legacy.wikibits&only=scripts&skin=vector&version=18kdz1s:161)
at execute (load.php?debug=false&lang=de&modules=jquery%2Cmediawiki|mediawiki.legacy.wikibits&only=scripts&skin=vector&version=18kdz1s:162)
at Object.implement (load.php?debug=false&lang=de&modules=jquery%2Cmediawiki|mediawiki.legacy.wikibits&only=scripts&skin=vector&version=18kdz1s:168)
at <anonymous>:19:170
at domEval (load.php?debug=false&lang=de&modules=jquery%2Cmediawiki|mediawiki.legacy.wikibits&only=scripts&skin=vector&version=18kdz1s:159)
at load.php?debug=false&lang=de&modules=jquery%2Cmediawiki|mediawiki.legacy.wikibits&only=scripts&skin=vector&version=18kdz1s:165
```
It seems that there is a programmer's bug in /Kartographer/modules/settings/settings.js
```
( function ( $, mw ) {
var mapServer = mw.config.get( 'wgKartographerMapServer' ),
forceHttps = mapServer[ 4 ] === 's',
config = L.mapbox.config;
config.REQUIRE_ACCESS_TOKEN = false;
config.FORCE_HTTPS = forceHttps;
config.HTTP_URL = forceHttps ? false : mapServer;
config.HTTPS_URL = !forceHttps ? false : mapServer;
}( jQuery, mediaWiki ) );
```
If `wgKartographerMapServer` is not set for whatever reason (mapServer is nil) then you cannot perform `mapServer[ 4 ] === 's'`.
It is unknown to me why this problem occurs only in Chrome-based browsers.