Use script.remove instead of removeChild for unity loader hook

[alexqhj]

Key changes:

• Updated the return value for non-browser environments and null loader URLs to undefined instead of an implicit return.
• Simplified script element removal by using the remove method instead of window.document.body.removeChild. Previous version would produce error if the node was not present, i.e. when unloading multiple instances.

[alexqhj]

Sorry I didn’t open a discussion beforehand. This fix was pretty urgent for our team so I went ahead and (hopefully) patched it. There might be a better approach, but I’m hoping this at least addresses the immediate issue. Would love your thoughts.

[alexqhj]

yeah sorry for the mess. I completely overengineered the issue at first, after spending time debugging. Realized script.remove() would gracefully attempt to remove the node without having to keep references to how many instances of the loader script was initialized.

[jeffreylanters]

No problem! Thank you very much for your valuable contributions! I'll releases these improvements soon!