Steps to reproduce:

Install clean version of DXP

Install symfony profile 

composer require --dev symfony/profiler-pack

go to backoffice and open content structure

clear cache php bin/console c:c

refresh content strucure page in the back office 

click on ibexa Dxp icon on profiler in debug bar 

hostname/_profiler/bd41b7?panel=ezpublish.debug.toolbar

see the error thrown

An exception has been thrown during the rendering of a template ("Notice: Undefined offset: 1").  

NB: This error occurs the very first time you request the page after cache cleared