Fix NPE on Stale Index in IndicesService (elastic#38891)

* Closes elastic#38845

Author: original-brownbear

server/src/main/java/org/elasticsearch/indices/IndicesService.java

@@ -882,6 +882,9 @@ public IndexMetaData verifyIndexIsDeleted(final Index index, final ClusterState
             final IndexMetaData metaData;
             try {
                 metaData = metaStateService.loadIndexState(index);
+                if (metaData == null) {
+                    return null;
+                }
             } catch (Exception e) {
                 logger.warn(() -> new ParameterizedMessage("[{}] failed to load state file from a stale deleted index, " +
                     "folders will be left on disk", index), e);