Error/warning highlights in code left behind after fixing

Do the following:
- have a master ink file called master.ink
- have an include called include.ink
- in include.ink, type something like `~foobar=true`
- you get a correct error display (as the VAR isn't declared anywhere)
- in master.ink, declare the VAR ('VAR foobar=false')
- switch back to include.ink. The warning icon is gone, but the line which it was on is still red. It will stay red until you quit/restart ink and open up the files again.