php8.1 plugin error

[vantky21415]

hi everyone,
i'm using plugin, "filters" in php 8.1. there is an error, "PHP Deprecated:  trim(): Passing null to parameter #1 ($string) of type string is deprecated in /web/mail/plugins/filters/filters.php on line 185". how can i solve this.

line 185 is like,    "$searchstring = trim(rcube_utils::get_input_value('_searchstring', rcube_utils::INPUT_POST, true));"


Also, there is another error, PHP Warning:  Uninitialized string offset -1 in //web/mail/program/actions/settings/folder_edit.php on line 87.
it is not plugin issue, but please help me.