The issue

When hovering over a nested block in select mode, the left border disappears. This issue also affects parent blocks when one of their children is selected in select mode. Basically, it affects any block that has a dashed outline.

How to reproduce

1. Create Columns block.
2. Insert blocks into of the columns.
3. While in select mode, select the Columns block.
4. Still in select mode, hover over the Column blocks.

Expected behavior

Nothing should happen when you hover over a nested block in select mode.

##Screenshots

Envrionment info

• WordPress 5.4-alpha-46797
• Gutenberg master as of bf6976b
• Using Dissenter browser 0.70 (based on Chromium 78)