Error when trying to deactivate

Hi, as my topic says i have an error when i try to deactivate the plugin. I use the free version. Heres a screenshot of the error message Screenshot by Lightshot (prnt.sc)
and here are more details from the message received :

?να σφ?λμα τ?που E_ERROR εντοπ?στηκε στη γραμμ? 161 του αρχε?ου /home/#######/public_html/wp-content/plugins/wp-optimize/vendor/rosell-dk/webp-convert/src/Convert/Converters/ImageMagick.php. Κωδικ?? σφ?λματο?: Uncaught Error: Call to undefined function WebPConvert\Convert\Converters\escapeshellarg() in /home/#######/public_html/wp-content/plugins/wp-optimize/vendor/rosell-dk/webp-convert/src/Convert/Converters/ImageMagick.php:161
Stack trace: 0 /home/#######/public_html/wp-content/plugins/wp-optimize/vendor/rosell-dk/webp-convert/src/Convert/Converters/ImageMagick.php(252): WebPConvert\Convert\Converters\ImageMagick->createCommandLineOptions() 1 /home/#######/public_html/wp-content/plugins/wp-optimize/vendor/rosell-dk/webp-convert/src/Convert/Converters/ConverterTraits/EncodingAutoTrait.php(57): WebPConvert\Convert\Converters\ImageMagick->doActualConvert() 2 /home/#######/public_html/wp-content/plugins/wp-optimize/vendor/rosell-dk/webp-convert/src/Convert/Converters/ConverterTraits/EncodingAutoTrait.php(95): WebPConvert\Convert\Converters\ImageMagick->convertTwoAndSelectSmallest() 3 /home/#######/public_html/wp-content/plugins/wp-optimize/vendor/rosell-dk/webp-convert/src/Convert/Converters/AbstractConverter.php(256): WebPConvert\Convert\Converters\ImageMagick->runActualConvert() 4 /home/#######/public_html/wp-content/plugins/wp-optimize/vendor/rosell-dk/webp-convert/src/Convert/Converters/AbstractConverter.php(295): WebPConvert\Convert\Converters\AbstractConverter->doConvertImplementation() 5 /home/#######/public_html/wp-content/plugins/wp-optimize/webp/class-wpo-webp-utils.php(55): WebPConvert\Convert\Converters\AbstractConverter->doConvert() 6 /home/#######/public_html/wp-content/plugins/wp-optimize/webp/class-wpo-webp-test-run.php(39): WPO_WebP_Utils::perform_webp_conversion() 7 /home/#######/public_html/wp-content/plugins/wp-optimize/webp/class-wp-optimize-webp.php(53): WPO_WebP_Test_Run::get_converter_status() 8 /home/#######/public_html/wp-content/plugins/wp-optimize/webp/class-wp-optimize-webp.php(19): WP_Optimize_WebP->set_converter_status() 9 /home/#######/public_html/wp-content/plugins/wp-optimize/webp/class-wp-optimize-webp.php(41): WP_Optimize_WebP->__construct() 10 /home/#######/public_html/wp-content/plugins/wp-optimize/wp-optimize.php(268): WP_Optimize_WebP::get_instance() 11 /home/#######/public_html/wp-content/plugins/wp-optimize/includes/class-wpo-deactivation.php(17): WP_Optimize->get_webp_instance() 12 /home/#######/public_html/wp-includes/class-wp-hook.php(324): WPO_Deactivation::actions() 13 /home/#######/public_html/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters() 14 /home/#######/public_html/wp-includes/plugin.php(517): WP_Hook->do_action() 15 /home/#######/public_html/wp-admin/includes/plugin.php(816): do_action() 16 /home/#######/public_html/wp-admin/plugins.php(209): deactivate_plugins() 17 {main}

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