"Create a new block" command isn't displayed if allowed types are created from Settings

Description

Fixed an issue in Settings where the Create a new block command was not displayed if allowed types were created from Settings.

Note: If a block type created from code was added to the Allowed content types, then the Create block command was displayed.

Steps to reproduce:

1. In Settings, create a block type called MenuItemBlock with some properties.
2. In Settings, create a block type called HeaderBlock.
3. Add a content area property to HeaderBlock, select Allowed Content Types = MenuItemBlock.
4. In Edit mode, create a block of type HeaderBlock. Only the Select Content command was displayed.