Wizard panels extend JPanel and implement WizardDescriptor.Panel. Classes must be split.
I have fix ready. Waiting for repository opening.
Integrated into 'main-golden', will be available in build *200902220201* on http://bits.netbeans.org/dev/nightly/ (upload may still be in progress)
User: Marek Slama <firstname.lastname@example.org>
Log: #158678: Remove override of java.awt.Component.isValid()