Fix TypeScript index error in devices page

src/app/(dashboard)/devices/page.tsx

@@ -126,7 +126,7 @@ export default function DevicesPage() {
       header: "Agent", 
       accessor: (row) => (
         <span className="text-xs text-slate-300">
-          {agentsMap[row.agent_uuid] || row.agent_uuid || "-"}
+          {row.agent_uuid ? (agentsMap[row.agent_uuid] || row.agent_uuid) : "-"}
         </span>
       ), 
       className: "w-[12%]"