Getting fatal error with PHP 8.1.17.

[Chetna1510]

Describe the bug

2023-04-18T23:36:43+00:00 CRITICAL Uncaught TypeError: Unsupported operand types: float + string in /home/lcdcnet/mantra.lcdc.co/wp-content/plugins/checkout-fees-for-woocommerce/includes/class-alg-wc-checkout-fees.php:555
Stack trace:
#0 /home/lcdcnet/mantra.lcdc.co/wp-content/plugins/checkout-fees-for-woocommerce/includes/class-alg-wc-checkout-fees.php(901): Alg_WC_Checkout_Fees->calculate_the_fee()
#1 /home/lcdcnet/mantra.lcdc.co/wp-content/plugins/checkout-fees-for-woocommerce/includes/class-alg-wc-checkout-fees.php(954): Alg_WC_Checkout_Fees->get_the_fee()
#2 /home/lcdcnet/mantra.lcdc.co/wp-content/plugins/checkout-fees-for-woocommerce/includes/class-alg-wc-checkout-fees.php(416): Alg_WC_Checkout_Fees->maybe_add_cart_fee()
#3 /home/lcdcnet/mantra.lcdc.co/wp-includes/class-wp-hook.php(308): Alg_WC_Checkout_Fees->add_gateways_fees()
#4 /home/lcdcnet/mantra.lcdc.co/wp-includes/class-wp-hook.php(332): WP_Hook->apply_filters()
#5 /home/lcdcnet/mantra.lcdc.co/wp-includes/plugin.php(517): WP_Hook->do_action()
#6 /home/lcdcnet/mantra.lcdc.co/wp-content/plugins/woocommerce/includes/class-wc-cart.php(1888): do_action()
#7 /home/lcdcnet/mantra.lcdc.co/wp-content/plugins/woocommerce/includes/class-wc-cart-totals.php(272): WC_Cart->calculate_fees()
#8 /home/lcdcnet/mantra.lcdc.co/wp-content/plugins/woocommerce/includes/class-wc-cart-totals.php(833): WC_Cart_Totals->get_fees_from_cart()
#9 /home/lcdcnet/mantra.lcdc.co/wp-content/plugins/woocommerce/includes/class-wc-cart-totals.php(145): WC_Cart_Totals->calculate_fee_totals()
#10 /home/lcdcnet/mantra.lcdc.co/wp-content/plugins/woocommerce/includes/class-wc-cart-totals.php(134): WC_Cart_Totals->calculate()
#11 /home/lcdcnet/mantra.lcdc.co/wp-content/plugins/woocommerce/includes/class-wc-cart.php(1401): WC_Cart_Totals->__construct()
#12 /home/lcdcnet/mantra.lcdc.co/wp-content/plugins/woocommerce/includes/class-wc-ajax.php(378): WC_Cart->calculate_totals()
#13 /home/lcdcnet/mantra.lcdc.co/wp-includes/class-wp-hook.php(308): WC_AJAX::update_order_review()
#14 /home/lcdcnet/mantra.lcdc.co/wp-includes/class-wp-hook.php(332): WP_Hook->apply_filters()
#15 /home/lcdcnet/mantra.lcdc.co/wp-includes/plugin.php(517): WP_Hook->do_action()
#16 /home/lcdcnet/mantra.lcdc.co/wp-content/plugins/woocommerce/includes/class-wc-ajax.php(96): do_action()
#17 /home/lcdcnet/mantra.lcdc.co/wp-includes/class-wp-hook.php(308): WC_AJAX::do_wc_ajax()
#18 /home/lcdcnet/mantra.lcdc.co/wp-includes/class-wp-hook.php(332): WP_Hook->apply_filters()
#19 /home/lcdcnet/mantra.lcdc.co/wp-includes/plugin.php(517): WP_Hook->do_action()
#20 /home/lcdcnet/mantra.lcdc.co/wp-includes/template-loader.php(13): do_action()
#21 /home/lcdcnet/mantra.lcdc.co/wp-blog-header.php(19): require_once('/home/lcdcnet/m...')
#22 /home/lcdcnet/mantra.lcdc.co/index.php(17): require('/home/lcdcnet/m...')
#23 {main}
thrown in /home/lcdcnet/mantra.lcdc.co/wp-content/plugins/checkout-fees-for-woocommerce/includes/class-alg-wc-checkout-fees.php on line 555

To Reproduce
Steps to reproduce the behavior:

1. On this site you can see the issue if you activate Payment Gateway Based Fees and Discounts for WooCommerce. If activating it doesn't immediately cause the issue, try to set up a global 2.5% fee in the plugin to all carts.

I was unable to replicate the issue but I think we can fix the error message.

Setting video - https://drive.google.com/file/d/11OOSQaL8jRFHN33Z18g_4SqRG2MJmHwm

Additional context
https://tychesoftwares.freshdesk.com/a/tickets/53460