Same problem here unfortunately.
Giving the variable a default value if no value is set resolves the error.
Steps to Resolve the Issue:
weather-atlas/includes/class-weather-atlas.php
Edit this file right above the 1020 line.
// Steps to Resolve the Issue: Define $url_units Early in the Code: Before the snippet you posted, ensure that $url_units is defined. This might be based on a setting in the plugin or a default value:
if ( !isset($url_units) ) {
$url_units = '?units=metric'; // Or whatever default makes sense
}
// Add the link or branding to the footer
if ( $random_url <= 4 )
{
echo "<a href='" . esc_url( $url . $url_units ) . "' title='" . esc_attr( ${'city_name_' . $language_root_wp} ) . ", " . esc_attr( $country_name_abbr ) . " - " . esc_attr( $title ) . "' style='color:" . esc_attr( $text_color ) . "'>";
echo "<span class='weather-atlas-footer-block'>";
echo esc_html( ${'city_name_' . $language_root_wp} ) . ", " . esc_html( $country_name_abbr );
echo "</span>";
echo " " . esc_html( strtolower( $title ) ) . " ▸";
echo "</a>";
}