Collapse these checks, too

Since we're tidying the map as we go, it's harder to reason about
whether the error is that the set is null versus if the set doesn't
contain one entry in particular, so treat those conditions as being
the same.

Author: joegallo

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/authz/accesscontrol/DocumentSubsetBitsetCache.java

@@ -415,12 +415,7 @@ public String toString() {
     void verifyInternalConsistency() {
         bitsetCache.keys().forEach(cacheKey -> {
             final Set<BitsetCacheKey> keys = keysByIndex.get(cacheKey.indexKey);
-            if (keys == null) {
-                throw new IllegalStateException(
-                    "Key [" + cacheKey + "] is in the cache, but there is no entry for [" + cacheKey.indexKey + "] in the lookup map"
-                );
-            }
-            if (keys.contains(cacheKey) == false) {
+            if (keys == null || keys.contains(cacheKey) == false) {
                 throw new IllegalStateException(
                     "Key [" + cacheKey + "] is in the cache, but the lookup entry for [" + cacheKey.indexKey + "] does not contain that key"
                 );