fix: do not pass ref into SlotClone component if children is a React.Fragment

[terrymun]

Description

This PR fixes the issue with consuming any Radix UI Primitive in React 19, which will throw the following error in the console (as reported in #3224):

The error seems to arise from not checking the type of the children prop, which could potentially be a React Fragment that does not accept ref prop.

Therefore, the ref prop is only conditionally added to the props of the <SlotClone> element if children is not of type React.Fragment.

[terrymun]

Hi @chaance, any idea if we could get this merged? That will fix a lot of the extraneous errors to those consuming React 19 with Radix :)

[V-iktor]

Currently waiting on this to be able to upgrade my project 🚀

[terrymun]

@V-iktor For the moment being I am simply using the modified <Slot> component (as per my PR) and configure it as an alias for my webpack's resolve.alias config:

webpack: (config) => {
  config.resolve = {
    ...config.resolve,
    alias: {
      ...config.resolve.alias,
      // TODO: Remove this shim once Radix fixes the issue with incorrect ref prop drilling
      //       https://github.com/radix-ui/primitives/issues/3224
      '@radix-ui/react-slot': path.resolve(__dirname, '/path/to/custom/slot.tsx'),
    },
  };

  return config;
},

If you're using another bundler/builder, you might need to consult their documentation on how to implement a similiar alias config. For example, Vite has a resolve.alias option: https://vite.dev/config/shared-options.html#resolve-alias