Outline color unexpectedly changes to black

[benjiwheeler]

@fsih's change #695 improved the experience of a user who decreases outline width to 0, making the outline color automatically become transparent.

One Question I still have is whether the overall experience is confusing for a user who chooses a color for the outline, decreases the outline width a few times, and then realizes they've gone all the way down to zero and goes back up to 1.

What would the user expect? I think they would expect the color they chose before to be the outline color again. However, this change makes the outline color become black whenever the width is 0 and becomes larger.

Ideally, I think we would keep track of the previous color and use it instead of defaulting to black.

[benjiwheeler]

Ran into this again, when deleting the line width to type in a different width.