Until JDK-4138921, `TextLayout` did not accept empty strings in the constructor. This limitation has been removed. However, there is a guard condition in `OutlineTextRenderer` which checks for an empty string before trying to use `TextLayout` which explicitly calls out this limitation in a code comment. We should remove the out-of-date comment but leave the check in as an optimization (see discussion in the PR comments for JDK-4138921).