train on custom dataset

hi i try to reproduce on my custom dataset,
i use "RealSR" settings to run, but got this error below from  
_File "main.py", line 27, in main
    solver.fit()_


_raise ValueError("empty range for randrange() (%d, %d, %d)" % (istart, istop, width))
ValueError: empty range for randrange() (0, -36, -36)_

anyone have idea about this error?
