Flyout auto-closes after creating a variable

[rachel-fenichel]

When making a variable with the “make a variable button” in the flyout, the flyout closes–so you have to reopen it to go get the block, even though you obviously want to go select the variable block immediately.
Probably triggered by an overly-eager hideChaff call

[BenHenning]

I need to check again, but I think #240 may fix this.