Block's Options popover extends off screen and items are inaccessible

[mapk]

Describe the bug
This has happened to me on more than one occasion. I'll add a block to the bottom of the document, but then decide to delete it. When I click the block's toolbar options, the popover appears, but I can't access the lower options. The popover extends off the screen. I try to scroll to see more, but that doesn't work.

To reproduce
Steps to reproduce the behavior:

1. Add some blocks to your document.
2. On the last block toward the bottom of the screen, add a block that is not the same height as the block popover.
3. Click into the block's popover to try and delete the block.
4. Observe that the popover extends below the bottom of the document and the last options can't be accessed.

Expected behavior
When at the bottom of the document, the popover should pop upward instead of downward.

Screenshots

Example 1

Example 2

Desktop (please complete the following information):

• OSX
• Firefox 68.0
• Gutenberg 6.1