Error with make_training_splits method

[gitttt-1234]

When runninglabels.make_training_splits() with sleap-io v'0.1.8', the generated splits seems to be inconsistent as below:

Source file: Labels(labeled_frames=1200, videos=1, skeletons=1, tracks=0, suggestions=0)

Splits: (Labels(labeled_frames=960, videos=1, skeletons=1, tracks=0, suggestions=0),
 Labels(labeled_frames=1, videos=1, skeletons=1, tracks=0, suggestions=0),
 Labels(labeled_frames=120, videos=1, skeletons=1, tracks=0, suggestions=0))

Notebook to recreate the error: https://colab.research.google.com/drive/1wnbrV8Yz6dakGV0ASqMoV94Pnvlg9LSL?usp=sharing

(Also for the sleap file in Y:\\talmo\\foundation-datasets\\mice\\sleap-mice_of\\labels.full.v043.pkg.slp)

Thanks!

[talmo]

This is now fixed in v0.1.9.