fix: NumberWithUnit error handling

src/NumberWithUnit/NumberWithUnit.jsx

@@ -4,7 +4,13 @@ import {useState} from "react";
 export default function NumberWithUnit({label, onChange, value, className}) {
 
 	const splitValues = function (fontSize) {
+
+		if( !fontSize ) {
+			return {size: "0", unit: "px"};
+		}
+
 		const match = fontSize.match(/^(\d+)([a-z%]+)$/i);
+
 		if (!match) {
 			return {size: "16", unit: "px"};
 		}