Array and string offset access syntax with curly braces is deprecated in PHP 7.4. Use square brackets instead.

Problem/Motivation

I catched a PHP7.4 notice deprecation

Array and string offset access syntax with curly braces is deprecated in PHP 7.4. Use square brackets instead.

../apachesolr_multilingual/apachesolr_multilingual.install 57
../apachesolr_multilingual/apachesolr_multilingual.module 362

Steps to reproduce

Switch to php7.4, check logs

Proposed resolution

I would suggest to apply a patch