Fix broker statistic updates

app/src/components/helper/useUpdateComponentWhenNodeUpdates.tsx

@@ -0,0 +1,17 @@
+import * as q from '../../../../backend/src/Model'
+import { useEffect, useState } from 'react'
+
+export function useUpdateComponentWhenNodeUpdates(node?: q.TreeNode<any>): number {
+  const [lastUpdate, setLastUpdate] = useState(0)
+  useEffect(() => {
+    if (!node) {
+      return
+    }
+    const updateComponent = () => setLastUpdate(Date.now())
+    node.onMerge.subscribe(updateComponent)
+    return function cleanup() {
+      node.onMerge.unsubscribe(updateComponent)
+    }
+  }, [node])
+  return lastUpdate
+}