Avoid cython error (but there should be a better way)

Author: seberg

hdbscan/_hdbscan_tree.pyx

@@ -725,8 +725,10 @@ cpdef tuple get_clusters(np.ndarray tree, dict stability,
     # if you do, change this accordingly!
     if allow_single_cluster:
         node_list = sorted(stability.keys(), reverse=True)
+        node_list = [int(n) for n in node_list]
     else:
         node_list = sorted(stability.keys(), reverse=True)[:-1]
+        node_list = [int(n) for n in node_list]
         # (exclude root)
 
     cluster_tree = tree[tree['child_size'] > 1]