make_note_features breaks for force_fixed_size=True and 'unknown_direction' in score

[sildater]

possible bug fix: correct naming in line 722 return "unknown_direction" to return "unknown_articulation"

reproduce:

import partitura as pt
part = pt.load_musicxml("beethoven_op002_no2_mv4.xml")[0] # zeilinger
nf = pt.musicanalysis.compute_note_array(part, feature_functions=["articulation_direction_feature"], force_fixed_size=True)

gives

--> 747         j = names.index(name)
    748     else:
    749         names[j] = name

ValueError: 'unknown_direction' is not in list