fix(445): render default block on empty editor

[gloaysa]

Description

On first render, if the editor is empty adds a default block.
If paddingBottom is not null or undefined, we use the value provided in styles (no longer making it a mandatory number that modifies CSSProperties interface and what is expected).

Fixes #452 #445

Type of change

Please tick the relevant option.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• I have performed a self-review of my own code
• I have commented on my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have checked my code and corrected any misspellings

Video showing the fix

Screen.Recording.2025-04-21.at.10.18.10.mov

[vercel]

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[Darginec05]

I'm not sure if it's good idea to manage the editor value inside the core package.
I think the manipulation of the value should be completely on the user's side

[gloaysa]

I see your point and makes sense. On the other hand, the user might not be aware of the tooling needed to build an empty block and just expect that when the editor is empty, it will display the placeholder (currently it only displays a blank space).

My current solution is also flawed, now that I think about it, since buildBlockData uses a Paragraph, and maybe the current editor doesn't have the Paragraph plugin installed.

Maybe add documentation explaining this is the expected behaviour and how to solve it? (is the reason behind #494 )