indexing error in prune_synapseless_branches

[jefferis]

hemibrain_clean_skeleton calls prune_synapseless_branches

https://github.com/flyconnectome/hemibrainr/blob/36f255878d9c8cbf256ad8b1c8f0dd746d384a8c/R/hemibrain_read_neurons.R#L183-L184

but this has a logic error where point indexes and identifiers are mixed. For example in the example below prune is filled with the contents of the PointNo column (i.e. identifiers in line 211) but then used to subscript the PointNo column in line 239

https://github.com/flyconnectome/hemibrainr/blob/36f255878d9c8cbf256ad8b1c8f0dd746d384a8c/R/hemibrain_read_neurons.R#L211-L241

In the example below this results in prune_synapseless_branches returning c(NA,NA,NA) for the axonic cable.

al.local.neurons="1702323386"
neurons = neuprintr::neuprint_read_neurons(al.local.neurons)
neurons.split = hemibrain_flow_centrality(neurons)
neurons.cleaned = hemibrain_clean_skeleton(neurons.split)

[jefferis]

This means that the example for hemibrain_clean_skeleton skeleton fails. This is a good example of code that should have a test (not necessarily with all the neurons in the example).

[alexanderbates]

I have started to fix this and make a test, but I need to think about what I want to achieve now with this function.