Error on Reporting

After logging into the AppWallAds in WordPress Dashboard, it throws an error – I have never been able to see any reports or whatsoever. /wp-admin/admin.php?page=wiziappappwall always show some kind of errors…

/var/www/mobirowser/appwall_reports/protected/controllers/AppStatsController.php(121)

 {
117                 $this->getDatesFromRange($params['daterange'],$fromDate,$toDate);
118             }
119             else
120             {
121                 $toDate = date('Y-m-d');
122                 $date = new DateTime();
123                 $date->sub(new DateInterval('P7D'));
124                 $fromDate  = $date->format('Y-m-d');
125             }
126         }

I’ve absolutely no time and date error on my website.

https://wordpress.org/plugins/interstitial-app-wall-ads-for-a-better-mobile-monetization/