fix: prevent division by zero in membership rate calculation

app/Lib/Helpers/StatsHelper.php

@@ -135,6 +135,11 @@ final class StatsHelper
             ->whereDate('created_at', '>=', $start)
             ->whereDate('created_at', '<=', $end)
             ->count();
+
+        if (!$employee) {
+            return 0;
+        }
+
         return round($registered / $employee * 100, 2);
     }