The launcher row's `on_click` selects the tab. Its child close glyph also has its own `on_click` that selects + closes. After the close, the click bubbled up to the row, which then tried to re-select the tab we just removed — usually a no-op but a wasted state churn that can race with the close in BrowserCore. Add `cx.stop_propagation()` after the close handler so the click ends at the close glyph.