Vector vertical and horizontal line costumes not showing on stage

[seotts]

Expected Behavior

If you draw a costume that is one vector horizontal or vertical line and the sprite is showing, the costume should show on the stage.

Actual Behavior

Vector costumes that consist only of one exactly vertical or horizontal line do not show on the stage. Line width, length, color, and position do not seem to matter. See this project as an example:
https://scratch.mit.edu/projects/302984170/editor/

Steps to Reproduce

Create a sprite and a new blank costume, in vector. Draw an exactly vertical or horizontal line by shift-clicking the line tool.

Operating System and Browser

Mac OS X 10.14, Chrome 73 and Firefox 66