Deprecated: strpos(): Non-string needles will be interpreted as strings

After update of the theme, my website crashed with this error: Deprecated: strpos(): Non-string needles will be interpreted as strings in the future. Use an explicit chr() call to preserve the current behavior in /public_html/shop/wp-content/plugins/ups-woocommerce-shipping-method/plugin-update-checker/Puc/v4p4/Plugin/UpdateChecker.php on line 641

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