Add fallback for phone number input

Make sure every change event returns a string.

categories/formatted/react/src/components/PhoneNumberInput/index.tsx

@@ -91,6 +91,7 @@ export const PhoneNumberInput = React.forwardRef<
   } = useProxyInput<PhoneNumberInputDerivedElement, Value>({
     forwardedRef,
     valueSetterFn: (v) => setPhoneNumber(v),
+    transformChangeHandlerArgs: (v) => (v ?? '') as unknown as Value,
   });
 
   const commonInputStyles = clsx(