Try to get rid of array error in RecommendationJob, a=chris

diff --git a/src/library/media_jobs/RecommendationJob.php b/src/library/media_jobs/RecommendationJob.php
index 87d8778d0..b05f15118 100644
--- a/src/library/media_jobs/RecommendationJob.php
+++ b/src/library/media_jobs/RecommendationJob.php
@@ -786,8 +786,9 @@ class RecommendationJob extends MediaJob
             foreach ($group_embeddings as $group_id => $group_embedding) {
                 L\crawlTimeoutLog("Have done $group_count many groups");
                 if (in_array($group_id, $exclude_group_ids) ||
-                    in_array($group_id, $user_groups[$user_id]) ||
-                    in_array($group_id, $user_group_impression[$user_id])) {
+                    in_array($group_id, ($user_groups[$user_id] ?? [])) ||
+                    in_array($group_id,
+                    ($user_group_impression[$user_id] ?? []))) {
                     continue;
                 }
                 $group_embedding = unpack("E*", $group_embedding);