Data with an axis of length of 0 infinite loops

[coderforlife]

Seems that if you gives the function an array where one of the axes lengths is 0 then the program goes into an infinite loop. The simple test case I found is:

dwtn([[]], 'haar')

But it is likely true about others as well, just haven't tested other situations.

[grlee77]

Thanks for reporting this. It looks like we need to add some kind of sensible error in this case.

I don't believe we currently have any length 0 test cases.

[coderforlife]

I accidentally did it while writing in an IPython notebook. It was an incomplete line and then I lost my session when I killed the process (not really much of a loss).

[grlee77]

Okay, this should be addressed by #506. There was a guard against this in the 1D case, but it was not being applied for >=2D data.

[coderforlife]

Great!