T14c, T15 review fixes: Tab steps past merges, empty charts lay out nothing, flat domains widen by size, pointed parts let go of shrunk data, signed waterfall totals, sunburst children take their share, today stays on the timeline

src/charts/flow.rs

@@ -229,6 +229,10 @@ impl RenderOnce for SankeyChart {
         let flows: Entity<Flows> =
             window.use_keyed_state((self.id.clone(), "flows"), cx, |_, _| Flows::default());
         let (bounds, hover) = (flows.read(cx).bounds, flows.read(cx).hover);
+        let hover = hover.filter(|hover| match hover {
+            Hover::Node(ix) => *ix < self.nodes.len(),
+            Hover::Link(ix) => *ix < self.links.len(),
+        });
         let theme = cx.theme();
         let (colors, sizes, rem) = (theme.colors.clone(), theme.chart(), window.rem_size());
         let pixels = |length: gpui::Rems| f32::from(length.to_pixels(rem));