Disable code actions on syntax errors

[anderseknert]

We can't evaluate or debug files with syntax errors, but it looks like we keep sending these from the server in that case, presumably from the last known good state, which sometimes makes them appear in weird locations. We should simply not return anything in this case.

Perhaps later on we can have those actions located before any syntax errors in the file remain and when clicked help the user understand more about the error... but it's likely better to show syntax errors in-lined like linter issues anyway. So let's just hide the actions for now.