fix: error prevention if data is null of empty

src/pages/schedule/schedule.component.ts

@@ -82,6 +82,11 @@ export class ScheduleComponent implements OnInit {
         throw error;
       }))
       .subscribe(x => {
+        if (x == undefined || x.length === 0) {
+          this.isLoadTable = false;
+          return;
+        }
+
         this.data = x;
         switch (data[0]) {
           case TabsSelect.Group: