CI for mediawiki/extensions/WikidataPageBanner.git is broken, specifically the noselenium job; example [console output](https://integration.wikimedia.org/ci/job/quibble-vendor-mysql-php72-noselenium-docker/101543/console) from [empty change](https://gerrit.wikimedia.org/r/c/mediawiki/extensions/WikidataPageBanner/+/713036):
```counterexample,lines=5
11:59:59 14 08 2021 09:59:59.654:DEBUG [middleware:source-files]: Requesting /load.php?modules=ext.echo.api%2Cdm%2Cinit&version=1lc63
11:59:59 14 08 2021 09:59:59.655:DEBUG [middleware:source-files]: Fetching /load.php
11:59:59 14 08 2021 09:59:59.656:DEBUG [proxy]: proxying request - /load.php?modules=ext.echo.api%2Cdm%2Cinit&version=1lc63 to 127.0.0.1:9412
11:59:59 INFO:backend.PhpWebserver:[Sat Aug 14 09:59:59 2021] 127.0.0.1:42912 [200]: /load.php?modules=ext.echo.api%2Cdm%2Cinit&version=1lc63
11:59:59 Chrome Headless 90.0.4430.212 (Linux x86_64) LOG: 'Exception in module-execute in module ext.WikidataPageBanner.positionBanner:'
11:59:59 Chrome Headless 90.0.4430.212 (Linux x86_64) WARN: TypeError: url.indexOf is not a function
11:59:59 TypeError: url.indexOf is not a function
11:59:59 at jQuery.fn.init.jQuery.fn.load (http://localhost:9876/load.php?modules=jquery%7Cmediawiki.base&version=9q0tz:138:28)
11:59:59 at http://localhost:9876/load.php?modules=color-picker%2CdataValues%2CdiffMatchPatch%2Cdompurify%7CdataValues.DataValue%2CTimeValue%2Cvalues%7Cext.WikidataPageBanner.positionBanner%7Cext.articleplaceholder.createArticle%7Cext.centralauth.ForeignApi%7Cext.cite.style%2Cstyles%2CvisualEditor%7Cext.cite.visualEditor.core%2Cdata%7Cext.eventLogging%7Cext.eventLogging.debug%7Cext.guidedTour.lib%2Cstyles%7Cext.guidedTour.lib.internal%7Cext.templateDataGenerator.data%7Cext.uls.common%2Ci18n%2Clanguagenames%2Cmediawiki%2Cmessages%2Cpreferences%2Cwebfonts%7Cext.visualEditor.data%2CmoduleIcons%2CmoduleIndicators%7Cjquery.animateWithEvent%2Cclient%2Ccolor%2Ccookie%2ChighlightText%2Ci18n%2Cinputautoexpand%2ClengthLimit%2CmakeCollapsible%2Cspinner%2Csuggestions%2Ctablesorter%2CtextSelection%2Cthrottle-debounce%2Ctipsy%2Cui%2Culs%2Cvalueview%7Cjquery.event.special.eachchange%7Cjquery.makeCollapsible.styles%7Cjquery.spinner.styles%7Cjquery.tablesorter.styles%7Cjquery.ui.commonssuggester%2Clanguagesuggester%2Csuggester%7Cjquery.uls.data%2Cgrid%7Cjquery.util.getDirectionality%7Cjquery.valueview.Expert%2CExpertExtender%2CExpertStore%7Cjquery.valueview.experts.CommonsMediaType%2CEmptyValue%2CGeoShape%2CGlobeCoordinateInput%2CMonolingualText%2CQuantityInput%2CStringValue%2CTabularData%2CTimeInput%2CUnDeserializableValue%7Cjquery.wikibase.entityselector%2Cwbtooltip%7Cjquery.wikibase.toolbar.styles%7Cmediawiki.ForeignApi%2CForeignStructuredUpload%2CForeignUpload%2CString%2CTitle%2CUpload%2CUri%2Capi%2Ccldr%2Ccookie%2Cexperiments%2Cinspect%2CjqueryMsg%2Clanguage%2CmessagePoster%7Cmediawiki.ForeignApi.core%7Cmediawiki.ForeignStructuredUpload.BookletLayout%7Cmediawiki.Upload.BookletLayout%7Cmediawiki.action.view.redirectPage%7Cmediawiki.diff.styles%7Cmediawiki.editfont.styles%7Cmediawiki.interface.helpers.styles%7Cmediawiki.language.months%2Cnames%2CspecialCharacters%2Ctestdata%7Cmediawiki.libs.guiders%2Cjpegmeta%2Cpluralruleparser%7Cmediawiki.page.gallery.styles%7Cmediawiki.page.ready&version=72fq8:90:739
11:59:59 at http://localhost:9876/load.php?modules=color-picker%2CdataValues%2CdiffMatchPatch%2Cdompurify%7CdataValues.DataValue%2CTimeValue%2Cvalues%7Cext.WikidataPageBanner.positionBanner%7Cext.articleplaceholder.createArticle%7Cext.centralauth.ForeignApi%7Cext.cite.style%2Cstyles%2CvisualEditor%7Cext.cite.visualEditor.core%2Cdata%7Cext.eventLogging%7Cext.eventLogging.debug%7Cext.guidedTour.lib%2Cstyles%7Cext.guidedTour.lib.internal%7Cext.templateDataGenerator.data%7Cext.uls.common%2Ci18n%2Clanguagenames%2Cmediawiki%2Cmessages%2Cpreferences%2Cwebfonts%7Cext.visualEditor.data%2CmoduleIcons%2CmoduleIndicators%7Cjquery.animateWithEvent%2Cclient%2Ccolor%2Ccookie%2ChighlightText%2Ci18n%2Cinputautoexpand%2ClengthLimit%2CmakeCollapsible%2Cspinner%2Csuggestions%2Ctablesorter%2CtextSelection%2Cthrottle-debounce%2Ctipsy%2Cui%2Culs%2Cvalueview%7Cjquery.event.special.eachchange%7Cjquery.makeCollapsible.styles%7Cjquery.spinner.styles%7Cjquery.tablesorter.styles%7Cjquery.ui.commonssuggester%2Clanguagesuggester%2Csuggester%7Cjquery.uls.data%2Cgrid%7Cjquery.util.getDirectionality%7Cjquery.valueview.Expert%2CExpertExtender%2CExpertStore%7Cjquery.valueview.experts.CommonsMediaType%2CEmptyValue%2CGeoShape%2CGlobeCoordinateInput%2CMonolingualText%2CQuantityInput%2CStringValue%2CTabularData%2CTimeInput%2CUnDeserializableValue%7Cjquery.wikibase.entityselector%2Cwbtooltip%7Cjquery.wikibase.toolbar.styles%7Cmediawiki.ForeignApi%2CForeignStructuredUpload%2CForeignUpload%2CString%2CTitle%2CUpload%2CUri%2Capi%2Ccldr%2Ccookie%2Cexperiments%2Cinspect%2CjqueryMsg%2Clanguage%2CmessagePoster%7Cmediawiki.ForeignApi.core%7Cmediawiki.ForeignStructuredUpload.BookletLayout%7Cmediawiki.Upload.BookletLayout%7Cmediawiki.action.view.redirectPage%7Cmediawiki.diff.styles%7Cmediawiki.editfont.styles%7Cmediawiki.interface.helpers.styles%7Cmediawiki.language.months%2Cnames%2CspecialCharacters%2Ctestdata%7Cmediawiki.libs.guiders%2Cjpegmeta%2Cpluralruleparser%7Cmediawiki.page.gallery.styles%7Cmediawiki.page.ready&version=72fq8:91:33
11:59:59 at runScript (http://127.0.0.1:9412//index.php?title=Special:JavaScriptTest/qunit/export:12:745)
11:59:59 at execute (http://127.0.0.1:9412//index.php?title=Special:JavaScriptTest/qunit/export:14:337)
11:59:59 at doPropagation (http://127.0.0.1:9412//index.php?title=Special:JavaScriptTest/qunit/export:6:488)
11:59:59 Chrome Headless 90.0.4430.212 (Linux x86_64) ERROR
11:59:59 Script error.
11:59:59 at :0:0
11:59:59 14 08 2021 09:59:59.754:DEBUG [Chrome Headless 90.0.4430.212 (Linux x86_64)]: CONFIGURING -> CONNECTED
11:59:59 14 08 2021 09:59:59.756:DEBUG [launcher]: CAPTURED -> BEING_KILLED
11:59:59 14 08 2021 09:59:59.757:DEBUG [launcher]: BEING_KILLED -> BEING_FORCE_KILLED
11:59:59 14 08 2021 09:59:59.757:DEBUG [Chrome Headless 90.0.4430.212 (Linux x86_64)]: CONNECTED -> DISCONNECTED
```
(Noticed on [this nonempty change](https://gerrit.wikimedia.org/r/c/mediawiki/extensions/WikidataPageBanner/+/712916) by @Samwilson.)
**Acceptance criteria 🏕️🌟(18 August 2021)**
[] CI is green (test passes) on master