forgot to fix the code error

Author: alexrockhill

frontend/src/components/UserSettings/Appearance.tsx

@@ -14,7 +14,7 @@ const Appearance = () => {
         </Heading>
 
         <RadioGroup
-          onValueChange={(e) => setTheme(e.value)}
+          onValueChange={(e) => setTheme(e.value ?? "system")}
           value={theme}
           colorPalette="teal"
         >