fixes #16

src/LarvaDatasets.jl

 module LarvaDatasets
 
-""" Generate *larva_dataset hdf5* files as introduced by MaggotUBA.
+""" Generate *larva_dataset* hdf5 files as introduced by MaggotUBA.
 
 This module exposes the default implementation and proceeds in 3 steps:
 
@@ -77,11 +77,12 @@ function labelcounts(files, headlength=nothing, taillength=nothing;
                 return
             end
             for (j, track) in enumerate(values(run))
+                timestamps = track.timestamps
                 track = track[:labels]
                 lock(c)
                 try
                     for k in headlength+1:length(track)-taillength
-                        t = track.timestamps[k]
+                        t = timestamps[k]
                         tags = track[k]
                         isnothing(selection_rule) || selection_rule(file.source, track.id, t, tags) || continue
                         for label in (tags isa Vector ? tags : [tags])