Notice: Trying to access array offset on value of type bool in the php

Is there a simple explanation for this error please? I’m getting this error after installing the premium version:

“Notice: Trying to access array offset on value of type bool in /home/u5236692/public_html/dunialingua.com/wp-content/plugins/material-design-for-contact-form-7-premium/public/cf7-material-design-custom-style.php on line 78”:

78 ( ! isset( $this->options[‘use_custom_styles’] ) ) ||

in context:

// Only print styles with PHP in premium
        if( $this->fs->is__premium_only() ) {
			if( $this->fs->can_use_premium_code() ) {
                
                // Only print custom styles if checkbox checked (even in pro)
                if(
                    is_array( $this->options ) &&
                    ( ! isset( $this->options['use_custom_styles'] ) ) ||
                    $this->options['use_custom_styles']
                ) {

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