Describe the bug
The Cover Block minimum height does not reflect the actual height of the cover block.

To reproduce

1. Create a Cover Block with a 3 column Columns block with an image per block
2. Using the mouse, shrink the height of the Cover block to less than the content height
3. Release the mouse button used to shrink the Cover Block window (the Cover Block window will snap back to the height of its content).

Expected behavior
The Minimum Height admin box should reflect the actual Cover Block height but it gets stuck on the smallest vertical height of the window shrink process in step2 above. See screenshot below.

NOTE: If you click the mouse on the bottom of the Cover Block window the Minimum Height admin box adjusts to the correct value.

Screenshots

Desktop (please complete the following information):
OS: Windows10
Browser Firefox
Version 69.0.3

Additional context

• Not using the GB plug-in. Using WP 5.3-beta3-46461
• Latest Twenty-Nineteen theme