Configure logger before using it

(cherry picked from commit 05d0f98)

Author: Kevinjil

webapp/src/Service/ExternalContestSourceService.php

@@ -200,6 +200,9 @@ public function getContestStartTime(): ?float
         if (isset($this->cachedContestData->startTime)) {
             return Utils::toEpochFloat($this->cachedContestData->startTime);
         } else {
+            if (empty($this->logger)) {
+                $this->configureLogger();
+            }
             $this->logger->warning('Contest has no start time, is the contest paused?');
             return null;
         }