Bump faf-stack version to v20.4.18 (#578)

* Adapt tests to faf-stackv20.4.18

Needed to remove all references to maps with id 0.

* Replace map id 0 with NULL instead

.travis.yml

@@ -13,7 +13,7 @@ before_install:
   - sudo /etc/init.d/mysql stop
   - git clone https://github.com/FAForever/faf-stack.git faf-stack
       && pushd faf-stack
-      && git checkout v20.2.7
+      && git checkout v20.4.18
       && export $(egrep -v '^#' .env.template | xargs)
       && cp -r config.template config
       && ./scripts/init-db.sh

tests/data/test-data.sql

@@ -323,7 +323,7 @@ insert into ban (player_id, author_id, reason, level, expires_at, revoke_time) v
 ;
 
 insert into game_stats (id, startTime, gameType, gameMod, host, mapId, gameName, validity) values
-    (41935, NOW(), '0', 6, 1, 0, 'MapRepetition', 0),
+    (41935, NOW(), '0', 6, 1, NULL, 'MapRepetition', 0),
     (41936, NOW() + interval 1 minute, '0', 6, 1, 1, 'MapRepetition', 0),
     (41937, NOW() + interval 2 minute, '0', 6, 1, 2, 'MapRepetition', 0),
     (41938, NOW() + interval 3 minute, '0', 6, 1, 3, 'MapRepetition', 0),