The appender in the group block is missing icon

[draganescu]

Describe the bug
While testing #19135 I noticed that the group block in Firefox 71 is missing the plus Icon (Chrome displays properly)

To reproduce
Steps to reproduce the behavior:

1. Use Firefox latest
2. Create a post
3. Add a group block
4. See bug

Expected behavior
The appender to have the plus icon

Screenshots

Desktop (please complete the following information):

• OS: osx
• Browser Firefox
• Version 71

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

[glendaviesnz]

Seems to be related to the .block-editor-button-block-appender styles.

If flex-direction: column is disabled it fixes it:

but this breaks the alignment in chrome

removing the padding also fixes it, and doesn't break the alignment in chrome:

Ran out of time to work out exactly what the issue is, or what the best fix is sorry.

[bartczyz]

Howdy @draganescu!

I noticed this issue on MacOS 10.14.6 / Safari 13.0.4 as well.

IMO the problem is with the height of the element. Since height is not set the element is being squashed by the padding.

Adding height: 100% fixes the problem for me.

I will open a PR later today. 👍