### 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 (backingIndexPosition == -1) {
            throw new IllegalArgumentException(
                String.format(Locale.ROOT, "index [%s] is not part of data stream [%s]", existingBackingIndex.getName(), name)
            );
        }
        if (indices.size() == (backingIndexPosition + 1)) {
            throw new IllegalArgumentException(
                String.format(
                    Locale.ROOT,
                    "cannot replace backing index [%s] of data stream [%s] because it is the write index",
                    existingBackingIndex.getName(),
                    name
                )
            );
        }
        backingIndices.set(backingIndexPosition, newBackingIndex);
        return new DataStream(name, backingIndices, generation + 1, metadata, hidden, replicated, system, allowCustomRouting, indexMode);
    }
    /**
     * Adds the specified index as a backing index and returns a new {@code DataStream} instance with the new combination
     * of backing indices.
     *
     * @param index index to add to the data stream
     * @return new {@code DataStream} instance with the added backing index
     * @throws IllegalArgumentException if {@code index} is ineligible to be a backing index for the data stream
     */
    public DataStream addBackingIndex(Metadata clusterMetadata, Index index) {
        
        final var parentDataStream = clusterMetadata.getIndicesLookup().get(index.getName()).getParentDataStream();
        if (parentDataStream != null) {