Fix no usage_summary for services not active yet, minor improvements to traffic graph

app/Models/Service/Adsl.php

@@ -136,9 +136,9 @@ class Adsl extends ServiceType implements ServiceItem,ServiceUsage
 	/**
 	 * Find the last date any traffic was recorded for a service
 	 *
-	 * @return AdslTraffic
+	 * @return AdslTraffic|null
 	 */
-	private function usage_last_date(): AdslTraffic
+	private function usage_last_date(): ?AdslTraffic
 	{
 		return $this->traffic
 			->sortBy('date')

resources/views/theme/backend/adminlte/u/service/widgets/broadband/usagegraph.blade.php

@@ -10,7 +10,7 @@
 					<thead>
 					<tr>
 						<th>Period</th>
-						<th class="text-right">Traffic</th>
+						<th class="text-right">Traffic <small>(GB)</small></th>
 					</tr>
 					</thead>
 					<tbody>
@@ -41,7 +41,10 @@
 
 		Highcharts.setOptions({
 			global: {
-				timezoneOffset: timezone
+				timezoneOffset: timezone,
+			},
+			lang: {
+				thousandsSep: ','
 			}
 		});