```name=Error Message
PHP Notice: Undefined index: start
```
also:
```
PHP Notice: Undefined index: end)
```
```lines=12,name=Stack Trace
#0 /srv/mediawiki/php-1.36.0-wmf.26/includes/specials/SpecialContributions.php(829): MWExceptionHandler::handleError(integer, string, string, integer, array)
#1 /srv/mediawiki/php-1.36.0-wmf.26/includes/specials/SpecialContributions.php(418): SpecialContributions->getPager()
#2 /srv/mediawiki/php-1.36.0-wmf.26/includes/specials/SpecialContributions.php(217): SpecialContributions->contributionsSub(User)
#3 /srv/mediawiki/php-1.36.0-wmf.26/includes/specialpage/SpecialPage.php(645): SpecialContributions->execute(NULL)
#4 /srv/mediawiki/php-1.36.0-wmf.26/includes/specialpage/SpecialPageFactory.php(1405): SpecialPage->run(NULL)
#5 /srv/mediawiki/php-1.36.0-wmf.26/includes/MediaWiki.php(310): MediaWiki\SpecialPage\SpecialPageFactory->executePath(Title, RequestContext)
#6 /srv/mediawiki/php-1.36.0-wmf.26/includes/MediaWiki.php(944): MediaWiki->performRequest()
#7 /srv/mediawiki/php-1.36.0-wmf.26/includes/MediaWiki.php(548): MediaWiki->main()
#8 /srv/mediawiki/php-1.36.0-wmf.26/index.php(53): MediaWiki->run()
#9 /srv/mediawiki/php-1.36.0-wmf.26/index.php(46): wfIndexMain()
#10 /srv/mediawiki/w/index.php(3): require(string)
#11 {main}
```
##### Impact
Presumably, paging doesn't work right on special:contributions under some circumstances
##### Notes
Seen 21 times within 10 minutes, all from wikidata. May be the same user hitting Special:Contributions some uncommon set of parameters (maybe by manipulating the URL?)
A brief look at the code led me to believe that the 'start' and 'end' fields in $this->opts may not be populated when $skip is set.