Error when increased features to N=3 of sample data for hdbscan

[sr248]

I got an error when I changed the code in quick_start.ipynb as following.

'''Apply HEADSS to evaluate the chosen data'''
merge = HEADSS.headss_merge(df = data, N = 3, split_columns = ['x', 'y', 'z'], merge = True,
                      cluster_columns=['x','y','z'], min_cluster_size = 10, 
                      min_samples = 10, cluster_method = 'leaf', allow_single_cluster = False,
                 total_threshold = 0.1, overlap_threshold = 0.5, minimum_members = 10) 

# clustering result
merged_df = merge.members_df

While debugging, it seems the register df holds no data of DataFrame in headss_merge.describe_clusters(). Here are the errors.

{
	"name": "ValueError",
	"message": "max() iterable argument is empty",
	"stack": "---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
Cell In[24], line 2
      1 '''Apply HEADSS to evaluate the chosen data'''
----> 2 merge = HEADSS.headss_merge(df = data, N = 3, split_columns = ['x', 'y', 'z'], merge = True,
      3                       cluster_columns=['x','y','z'], min_cluster_size = 10, 
      4                       min_samples = 10, cluster_method = 'leaf', allow_single_cluster = False,
      5                  total_threshold = 0.1, overlap_threshold = 0.5, minimum_members = 10) 
      7 # clustering result
      8 merged_df = merge.members_df

File /work/HEADSS/code/HEADSS.py:698, in headss_merge.__init__(self, N, df, split_columns, cluster_columns, df_clustered, stitch_regions, min_cluster_size, min_samples, cluster_method, allow_single_cluster, merge, total_threshold, overlap_threshold, minimum_members)
    696 self.overlap_threshold = overlap_threshold
    697 print('check1')
--> 698 self.members_df = self.mergeClusters()

File /work/HEADSS/code/HEADSS.py:851, in headss_merge.mergeClusters(self)
    849 df = self.members_df
    850 print('check2')
--> 851 cluster_info = self.describe_clusters()
    852 matches = self.find_overlapping_clusters(cluster_info = cluster_info[:])
    853 cluster_merges = self.check_cluster_merge(matches = matches)

File /work/HEADSS/code/HEADSS.py:716, in headss_merge.describe_clusters(self, group_col)
    714 groups = df[group_col].unique()
    715 print('groups:', groups)
--> 716 cluster_info = np.zeros(int(max(groups)+1), dtype = object)
    717 print('cluster_info:', cluster_info)
    718 for index, group in enumerate(groups):

ValueError: max() iterable argument is empty"
}

Could you please check on this? Thank you!