Erreurs 500 dans les logs

En fouillant les logs, je vois cette erreur ;

Fri, 27 Nov 2020 11:37:03 +0100 [194.50.] 500 - Undefined variable: block_content
Fri, 27 Nov 2020 11:37:03 +0100 [194.50.] [/home/don/don/vendor/sentry/sentry/lib/Raven/Breadcrumbs/ErrorHandler.php:34] Base->{closure}()
Fri, 27 Nov 2020 11:37:03 +0100 [194.50.] [/home/don/don/vendor/sentry/sentry/lib/Raven/ErrorHandler.php:127] Raven_Breadcrumbs_ErrorHandler->handleError()
Fri, 27 Nov 2020 11:37:03 +0100 [194.50.] [/home/don/don/tmp/31ltv25t12ckk.2dzdna38z3okc.php:116] Raven_ErrorHandler->handleError()
Fri, 27 Nov 2020 11:37:03 +0100 [194.50.] [/home/don/don/tmp/31ltv25t12ckk.23gny3ijc6g0o.php:5] Preview->render()
Fri, 27 Nov 2020 11:37:03 +0100 [194.50.] [/home/don/don/app/controller/controller.php:140] Preview->render()
Fri, 27 Nov 2020 11:37:03 +0100 [194.50.] [index.php:71] Base->run()

Elle est présente de nombreuses fois.