early return if no help defined (rjsf-team#4816)

When `fieldPathId` is undefined, `helpId` will throw an undefined value error.

The other `FieldHelpTemplate.tsx` files guard against this with an early return.

Found this while trying the Mantine theme with a quickstart/simple string schema and it would not load the form because of this.

Author: adrobisch

packages/mantine/src/templates/FieldHelpTemplate.tsx

@@ -12,9 +12,13 @@ export default function FieldHelpTemplate<
 >(props: FieldHelpProps<T, S, F>) {
   const { fieldPathId, help } = props;
 
+  if (!help) {
+    return null;
+  }
+
   const id = helpId(fieldPathId);
 
-  return !help ? null : (
+  return (
     <Text id={id} size='sm' my='xs' c='dimmed'>
       {help}
     </Text>