MST/AIM output can include None values

[madprogramer]

Consider a dataset dat with only 3 binary variables (encoded using the LabelTransformer)

A	B	C
1	0	1
0	0	1
1	1	1
1	1	1

When I call synth.fit_sample(dat, transformer=tableTransformer) I seemingly get no errors for MST/AIM synthesizers. However, upon inspecting the input it looks a little something like this:

A	B	C
1	1	1
1	1	None
None	None	1
0	0	1

I don't suppose there is an easy fix for this, besides increasing sample size/epsilon. But at the very least I think fit_sample should generate a warning when None values are present.