Fix Plotly preview crash and streamline README note

README.md

@@ -40,18 +40,4 @@ For full production setup (Traefik + DNS + Plausible CE + maintenance), see [PRO
 ### Notes
 - Linting: `npm run lint`.
 - If the map on the landing page does not render, ensure WebGL is available/enabled in your browser.
-
-## PR preview deployments
-
-This repository includes a GitHub Actions workflow (`.github/workflows/pr-preview.yml`) that:
-- triggers on PR `opened`, `synchronize`, and `reopened`;
-- builds the app with `npm ci` and `npm run build`;
-- deploys the built `dist/` to `gh-pages` under `pr-<PR_NUMBER>/`;
-- creates or updates a PR comment with the preview URL;
-- on PR close, updates that comment to mark the preview as no longer maintained (lightweight cleanup).
-
-Expected preview URL format:
-`https://<owner>.github.io/<repo>/pr-<PR_NUMBER>/`
-
-Repository setting required once:
-- **Settings → Pages**: source must be the `gh-pages` branch (root folder).
+- PR website preview builds are deployed automatically via GitHub Actions at `https://ai4up.github.io/cities-learning-explorer/pr-<PR#>/`.

src/components/TypeMetricsPlot.jsx

@@ -147,17 +147,25 @@ const TypeMetricsPlot = ({ cities, activeType }) => {
       };
     });
 
-    Plotly.newPlot(plotRef.current, traces, layout, {
+    const plotElement = plotRef.current;
+
+    Plotly.newPlot(plotElement, traces, layout, {
       displayModeBar: false,
       responsive: true,
     });
 
-    const resize = () => Plotly.Plots.resize(plotRef.current);
+    const resize = () => {
+      if (plotElement) {
+        Plotly.Plots.resize(plotElement);
+      }
+    };
     window.addEventListener("resize", resize);
 
     return () => {
       window.removeEventListener("resize", resize);
-      Plotly.purge(plotRef.current);
+      if (plotElement) {
+        Plotly.purge(plotElement);
+      }
     };
   }, [cities, activeType]);