Incorrect styling of some failed expressions

[pdubroy]

Here's a screenshot from the latest version:

This is with the arithmetic grammar, and the input 1+2*3-. Here's what it should look like:

Note a couple of problems:

• The top-level Exp succeeded, why is it pink?
• AddExp_plus, AddExp_minus, and MulExp are missing the disclosure arrows (this is probably related to vbox/isInVBox)

[pdubroy]

Also, I noticed that we no longer have the [Grow LR] expression.

[lilyx]

Solved by 0edb5f9