Describe the bug

I can't delete images using the keyboard only when coming from below.

To Reproduce
Steps to reproduce the behavior:

1. Create a post with an image and add a bit of text after it
2. Place the cursor at the end of the text and backspace until the paragraph is empty
3. Backspace once to remove the paragraph
4. Backspace again from the image block

Expected behavior

I'd expect the last backspace (with the image selected) would remove the image.
Instead, the cursor is stuck on the caption and backspace does nothing.

Screenshots

Desktop (please complete the following information):

• OS: macOS
• Browser Safari
• Version 11.1.1

Additional context

• Tested in Gutenberg 3.0.1