ChangeCheckerImpl: Fix null guard check

The null guard check for the metaSha was wrong. This was actually
correct in the past and the mistake was introduced with
Ie45c2f1e209952ae7f2a91dc6b65c0c153f48376.

Change-Id: I302e54c238891ab8e1c37ecc77618e6d77c60381

src/main/java/com/ericsson/gerrit/plugins/highavailability/index/ChangeCheckerImpl.java

diff --git a/src/main/java/com/ericsson/gerrit/plugins/highavailability/index/ChangeCheckerImpl.java b/src/main/java/com/ericsson/gerrit/plugins/highavailability/index/ChangeCheckerImpl.java
index 6156fb5..e4de705 100644
--- a/src/main/java/com/ericsson/gerrit/plugins/highavailability/index/ChangeCheckerImpl.java
+++ b/src/main/java/com/ericsson/gerrit/plugins/highavailability/index/ChangeCheckerImpl.java
@@ -102,7 +102,7 @@
           IndexEvent indexEvent = indexEventOption.get();
           return computedChangeTs.get().compareTo(indexEvent.eventCreatedOn) >= 0
               && (Objects.isNull(indexEvent.targetSha) || repositoryHas(repo, indexEvent.targetSha))
-              && (Objects.isNull(indexEvent.targetSha) || repositoryHas(repo, indexEvent.metaSha));
+              && (Objects.isNull(indexEvent.metaSha) || repositoryHas(repo, indexEvent.metaSha));
         }
       }
       return true;