Seems to only be observed on commons.wikimedia.org
Steps to replicate the issue (include links if applicable):
1283 errors in the last 7 days
https://logstash.wikimedia.org/goto/ec6c2d2beefcfe546fb63ecf8ff03149
Observed only on https://commons.wikimedia.org/wiki/Special:UploadWizard
Stack trace:
at UWSingleLanguageInputWidget/< https://commons.wikimedia.org/w/load.php?lang=es&modules=ext.uploadWizard%7Cext.uploadWizard.page&skin=vector&version=puvic:166:150 at OO.EventEmitter.prototype.emit https://commons.wikimedia.org/w/load.php?lang=es&modules=oojs&skin=vector&version=rwdvu:8:344 at uw.UlsWidget.prototype.setValue https://commons.wikimedia.org/w/load.php?lang=es&modules=ext.uploadWizard%7Cext.uploadWizard.page&skin=vector&version=puvic:164:674 at onSelect https://commons.wikimedia.org/w/load.php?lang=es&modules=ext.uploadWizard%7Cext.uploadWizard.page&skin=vector&version=puvic:163:972 at select https://commons.wikimedia.org/w/load.php?lang=es&modules=jquery.uls&skin=vector&version=1c2o4:23:632 at listen/< https://commons.wikimedia.org/w/load.php?lang=es&modules=jquery.uls&skin=vector&version=1c2o4:39:977 at dispatch https://commons.wikimedia.org/w/load.php?lang=es&modules=jquery%2Cmoment%2Coojs-ui-core%7Cmediawiki.feedback%2CmessagePoster%7Cmediawiki.libs.jpegmeta%7Cmediawiki.widgets.CategoryMultiselectWidget%2CDateInputWidget%2Cstyles%7Cmediawiki.widgets.DateInputWidget.styles&skin=vector&version=1ahqn:65:932 at add/elemData.handle https://commons.wikimedia.org/w/load.php?lang=es&modules=jquery%2Cmoment%2Coojs-ui-core%7Cmediawiki.feedback%2CmessagePoster%7Cmediawiki.libs.jpegmeta%7Cmediawiki.widgets.CategoryMultiselectWidget%2CDateInputWidget%2Cstyles%7Cmediawiki.widgets.DateInputWidget.styles&skin=vector&version=1ahqn:62:565