this is a good advice.
im nevertheless not sure how to solve this problem:
A database query error has occurred. This may indicate a bug in the software.
Query:
UPDATE `ipblocks` SET ipb_user = '149',ipb_address = 'ZinaidaBryson' WHERE ipb_user = '350'
Function: UserMerge::mergeUser
Error: 1062 Duplicate entry 'ZinaidaBryson-149-0-0' for key 'ipb_address' (localhost)
Backtrace:
#0 /var/www/web/html/wiki/includes/db/Database.php(1123): DatabaseBase->reportQueryError('Duplicate entry...', 1062, 'UPDATE `ipbloc...', 'UserMerge::merg...', false)
#1 /var/www/web/html/wiki/includes/db/Database.php(1986): DatabaseBase->query('UPDATE `ipbloc...', 'UserMerge::merg...')
#2 /var/www/web/html/wiki/extensions/UserMerge/UserMerge_body.php(434): DatabaseBase->update('ipblocks', Array, Array, 'UserMerge::merg...')
#3 /var/www/web/html/wiki/extensions/UserMerge/UserMerge_body.php(260): UserMerge->mergeUser(Object(User), 'ZinaidaBryson', '149', Object(User), 'Abbotthcfo', '350')
#4 /var/www/web/html/wiki/includes/specialpage/SpecialPage.php(379): UserMerge->execute(NULL)
#5 /var/www/web/html/wiki/includes/specialpage/SpecialPageFactory.php(503): SpecialPage->run(NULL)
#6 /var/www/web/html/wiki/includes/Wiki.php(285): SpecialPageFactory::executePath(Object(Title), Object(RequestContext))
#7 /var/www/web/html/wiki/includes/Wiki.php(588): MediaWiki->performRequest()
#8 /var/www/web/html/wiki/includes/Wiki.php(447): MediaWiki->main()
#9 /var/www/web/html/wiki/index.php(46): MediaWiki->run()
#10 {main}