Edge Bundling can have divide by zero errors

[kalebruscitti]

Running either of the plotting functions with bundling on sometimes yields:

site-packages/datashader/bundling.py:182: RuntimeWarning: invalid value encountered in divide img /= np.max(img)

Can be reproduced with the AI arXiv dataset, with

clusterer = HDBSCAN(cluster_selection_method='leaf') TM = tm.TemporalMapper( time, map_data, clusterer, N_checkpoints = 14, kernel=tmwc.square )