Fix NPE on Stale Index in IndicesService (#39174)

This is a backport of  #38891 which closes #38845

Author: jkakavas

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

@@ -900,6 +900,9 @@ 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);