Can't run test of seg_ctc_ent_log_fb.py file with Pytorch 1.2

[AndiezPham]

Hi @liuhu-bigeye,
When I try to test seg_ctc_ent_log_fb.py with Pytorch 1.2, I have an issue of RuntimeError: one of the variables needed for gradient computation has been modified by an inplace operation: [torch.FloatTensor [23, 20, 12]], which is output 0 of SliceBackward, is at version 50; expected version 48 instead.
This error comes from line 162 to line 166 of seg_ctc_ent_log_fb.py (blank_dev branch)
Can you help me refactor this code for Pytorch 1.2!
Thanks you so much!!