Violin plots fail when empty array is included among violin data

[JS3xton]

The following code fails using commit bc98686 (a few commits upstream of when plot-violin was merged into develop):

>>> FlowCal.plot.violin(data=[[1,2,3],[],[4,5,6]])

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\sexto\.conda\envs\py3_anaconda2020.07_fc_JS3xton_bc98686\lib\site-packages\flowcal-1.2.2-py3.8.egg\FlowCal\plot.py", line 1753, in violin
  File "<__array_function__ internals>", line 5, in amin
  File "C:\Users\sexto\.conda\envs\py3_anaconda2020.07_fc_JS3xton_bc98686\lib\site-packages\numpy\core\fromnumeric.py", line 2792, in amin
    return _wrapreduction(a, np.minimum, 'min', axis, None, out,
  File "C:\Users\sexto\.conda\envs\py3_anaconda2020.07_fc_JS3xton_bc98686\lib\site-packages\numpy\core\fromnumeric.py", line 90, in _wrapreduction
    return ufunc.reduce(obj, axis, dtype, out, **passkwargs)
ValueError: zero-size array to reduction operation minimum which has no identity

The error comes from using np.min() to calculate defaults limits for the data axis:

        data_min = np.inf
        data_max = -np.inf
        for idx in range(data_length):
            violin_data = np.array(data[idx], dtype=np.float).flat
            violin_min = np.min(violin_data)  # <-- fails here
            violin_max = np.max(violin_data)
            if violin_min < data_min:
                data_min = violin_min
            if violin_max > data_max:
                data_max = violin_max
        data_lim = (data_min, data_max)

np.min() fails when called on an empty array.

[JS3xton]

Fixed in FlowCal v1.3.0.

[JS3xton]

FlowCal.plot.violin(data=[[1,2,3],[],[4,5,6]]) still fails in v1.3.0 with the following error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/jsexton/Downloads/FlowCal-master/FlowCal/plot.py", line 1810, in violin
    t = _LogicleTransform(data=data, channel=channel)
  File "/home/jsexton/Downloads/FlowCal-master/FlowCal/plot.py", line 271, in __init__
    if d.ndim > 1:
AttributeError: 'list' object has no attribute 'ndim'