Fix site editor rendering of Categories block

[sunyatasattva]

What?

The Categories block would not render properly within the site editor. Specifically:

• Prefix and Suffix options were not shown when the block was selected.
• Separator was not available in the advanced panel.
• Alignment toolbar was not available in the toolbar.

Why?

#48940 reported the issue of missing the alignment toolbar. As I was investigating that, I found out a few more things were missing.

How?

The component was returning early in case no postId was found. Since no postId is present in the site editor, the early return was triggered. This PR makes sure that even in case we are in the site editor, we still output all the inspector controls, toolbars and prefix/suffix.

Testing Instructions

1. Go to the Site Editor.
2. Edit a Single Post template.
3. Add the Categories block.
4. Make sure that:
5. Text alignment options are available in the toolbar.
6. Prefix and suffix are available when the block is selected.
7. Separator is available in the inspector controls (under “Advanced”).
8. There is no loading state.
9. Still shows the “Categories” placeholder.
10. Go to the Post Editor.
11. Add the Categories block.
12. Make sure that:
13. There is a loading state.
14. Shows the correct categories.

[mikachan]

This is working well for me - it makes sense to move this logic into the main return statement with all the other conditional content.

Here is what I see in the Site Editor:

Before	After

I think we can bring this in! 🚢

[sunyatasattva]

Hello @mikachan @mirka and @apeatling I don't have merge authorization, so what can we do to bring this PR in?

[mikachan]

I don't have merge authorization, so what can we do to bring this PR in?

I can merge this for you. Thank you for working on it! 🙇