In `@src/main/java/com/flowingcode/vaadin/addons/demo/DynamicTheme.java`:
- Around line 70-73: The calls to VaadinSession.getCurrent() in
isFeatureInitialized(), getCurrent(), and initialize() can be null and cause
NPEs; update each method to first retrieve VaadinSession session =
VaadinSession.getCurrent() and guard against null (e.g., return false from
isFeatureInitialized(), return null or throw a clear IllegalStateException from
getCurrent(), and no-op or delay initialization in initialize()) before
accessing session.getAttribute(...) or session.setAttribute(...), preserving
existing behavior when session is present and adding a clear, defensive early
return when it's absent.
- Around line 166-178: The injected JS in component.getElement().executeJs calls
document.startViewTransition and then accesses properties on link without
verifying link exists, which can throw in non-Chromium browsers or when the
stylesheet isn't present; update the script to first check that
document.startViewTransition is a function and fall back to executing the
transition callback directly if unavailable, and add a null check for link
(e.g., if (link) { ... }) before reading or writing link.rel or link.disabled
when iterating over the href list (note the passed href parameter $0), so the
code safely handles missing <link> elements and browsers without
startViewTransition support.