### Elasticsearch Version

master

### Installed Plugins

_No response_

### Java Version

_bundled_

### OS Version

all

### Problem Description

cat indices API in time_series mode is NPE, The reproduce steps is below:

### Steps to Reproduce

```
# step 1
PUT _index_template/test
{
  "index_patterns": [
    "test"
  ],
  "template": {
    "settings": {
      "index.routing_path": "foo"
    },
    "mappings": {
      "properties": {
        "foo": {
          "type": "keyword",
          "time_series_dimension": true
        }
      }
    }
  },
  "data_stream": {
    "index_mode": "time_series"
  }
}

# step 2
PUT _data_stream/test

# step 3
GET _cluster/state/metadata/test
GET _cat/indices/test?v
```
server/src/main/java/org/elasticsearch/cluster/metadata/DataStream.java
if (parentDataStream.getDataStream().equals(this)) {
                return this;
            } else {
                throw new IllegalArgumentException(
                    String.format(
                        Locale.ROOT,
                        "cannot add index [%s] to data stream [%s] because it is already a backing index on data stream [%s]",
                        index.getName(),
                        getName(),
                        parentDataStream.getName()
                    )
                );
            }
        }
        
        IndexMetadata im = clusterMetadata.index(clusterMetadata.getIndicesLookup().get(index.getName()).getWriteIndex());
        if (im.getAliases().size() > 0) {
            throw new IllegalArgumentException(
                String.format(
                    Locale.ROOT,
                    "cannot add index [%s] to data stream [%s] until its alias(es) [%s] are removed",
                    index.getName(),
                    getName(),
                    Strings.collectionToCommaDelimitedString(im.getAliases().keySet().stream().sorted().toList())
                )
            );
        }
        List<Index> backingIndices = new ArrayList<>(indices);
        backingIndices.add(0, index);
        assert backingIndices.size() == indices.size() + 1;