In-between inserter: Unexpected vertical inserter display

[t-hamano]

Description

In #56186, a vertical inserter was introduced to create Rows and Galleries. However, this causes unintended behavior in some scenarios.

For example, we should consider the following scenarios:

• Group block is not registered
• Row variation is not registered
• Gallery block is not registered
• Cannot be wrapped in a Row block

Step-by-step reproduction instructions

From what I have seen, the scenarios that cause the problem are:

Create galleries from Image blocks

If both the Gallery block and the Row variation are not enabled:

• Expected: The inserter should not be displayed
• Actual: ❌ The inserter is displayed and you will get a browser console error like this once the drop is complete:

Uncaught Error: Block type 'core/gallery' is not registered.`

bafbe834b30aa1f641af2cfbac8fd31a.mp4

Create Rows from selected blocks

If the Row variation is not enabled:

• Expected: The inserter should not be displayed
• Actual: ❌ The inserter is displayed and the Row block with layout.type as flex appears to be created correctly, but the block name remains Group.

e9c94d89c8f0d666951faa9ca5ec765b.mp4

When a Row block cannot be created

For example, if the button orientation is vertical:

• Expected: Since we cannot create a Row block from the Button block (not the Buttons block), the inserter itself should not be displayed.
• Actual: ❌ The inserter appears. Buttons get duplicated and/or the browser freezes.

7429af61470d499fda765f06e29c186b.mp4

Screenshots, screen recording, code snippet

No response

Environment info

No response

Please confirm that you have searched existing issues in the repo.

• Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

• Yes