chore: keep error message centering

* address concerns of @silverwind and in case of an error add
  'display: flex' to the heatmap element, resulting in a nicely centered
  error message (since we kept the centering attributes in heatmap.less)

Author: wULLSnpAXbWZGYDYyhWTKKspEQoaYxXyhoisqHf

web_src/js/features/heatmap.js

@@ -18,6 +18,7 @@ export default async function initHeatmap() {
     new View().$mount(el);
   } catch (err) {
     console.error(err);
+    el.style.display = "flex";
     el.textContent = 'Heatmap failed to load';
   }
 }