Crashed block z-index problem with add new block button

[johngodley]

Describe the bug

If a block crashes it shows a crashed block warning. There is some z-index issue with this and the inline 'add new block' button:

To Reproduce
Steps to reproduce the behavior:

1. In dev console enter wp.blocks.registerBlockType( 'myplugin/mr-crashy', { title: 'Mr. Crashy', category: 'common', icon: 'warning', edit() { throw new Error(); }, save() { return ''; } } );
2. Add Mr Crashy block
3. Note that the inline block add buttons appear under the crash warning

Expected behavior
The inline block buttons should appear over the crash warning

There's also a slight overlap in the crash warning that can be fixed by changing block-list/style.scss with:

.editor-block-list__layout .editor-block-list__block {
	&.has-warning {
		min-height: ( $block-padding + $block-spacing ) * 2;
	}

[johngodley]

Closing as fixed