diff --git a/resources/views/theme/backend/adminlte/service/widget/billinghistory.blade.php b/resources/views/theme/backend/adminlte/service/widget/billinghistory.blade.php
index 6bb7dcb..431d8a5 100644
--- a/resources/views/theme/backend/adminlte/service/widget/billinghistory.blade.php
+++ b/resources/views/theme/backend/adminlte/service/widget/billinghistory.blade.php
@@ -15,8 +15,8 @@
 	@foreach($o->invoiced_items_active->groupBy('invoice_id') as $oo)
 		<tr>
 			<td><a href="{{ url('u/invoice',($x=$oo->first())->invoice_id) }}">{{ $x->invoice_id }}</a></td>
-			<td>{{ ($y=$oo->where('item_type',0))->min('start_at')->format('Y-m-d') }}</td>
-			<td>{{ $y->max('stop_at')->format('Y-m-d') }}</td>
+			<td>{{ ($y=$oo->where('item_type',0))->min('start_at')?->format('Y-m-d') }}</td>
+			<td>{{ $y->max('stop_at')?->format('Y-m-d') }}</td>
 			<th>{{ number_format($y->sum('total'),2) }}</th>
 			<th>{{ number_format($oo->where('item_type','<>',0)->sum('total'),2) }}</th>
 			<td class="text-right">{{ number_format($oo->sum('total'),2) }}</td>