try to get string_Add to work in recommendation job by adding a cast, a=chris

diff --git a/src/library/media_jobs/RecommendationJob.php b/src/library/media_jobs/RecommendationJob.php
index fe65d10ba..2e80b7124 100644
--- a/src/library/media_jobs/RecommendationJob.php
+++ b/src/library/media_jobs/RecommendationJob.php
@@ -487,9 +487,10 @@ class RecommendationJob extends MediaJob
         $condition = "ITEM_TYPE = ? AND USER_ID <> 2 AND" .
             " ((UPDATE_PERIOD = ? AND UPDATE_TIMESTAMP = ?) OR" .
             " (UPDATE_PERIOD = ?))";
-        $impression_sql = "SELECT USER_ID, $db_list_function(ITEM_ID, ',') AS" .
-            " ITEM_IDS FROM ITEM_IMPRESSION_SUMMARY WHERE $condition" .
-            " GROUP BY USER_ID";
+        $impression_sql = "SELECT USER_ID, ".
+            "$db_list_function(CAST(ITEM_ID AS STRING), ',') AS " .
+            "ITEM_IDS FROM ITEM_IMPRESSION_SUMMARY WHERE $condition " .
+            "GROUP BY USER_ID";
         $results = $db->execute($impression_sql,
             [C\THREAD_IMPRESSION, self::UPDATE_PERIOD, $timestamp,
                 C\MOST_RECENT_VIEW]);