Forward breaks with pytorch 1.4.0

[bearpaw]

Hi there,

recently I upgraded the pytorch to 1.4.0 and the forward function of pointnet2 broke with errors like:
CUDA: an illegal memory access was encountered.
or
CUDA kernel failed : no kernel image is available for execution on the device
And I am pretty sure it works well with the 1.2.0 conda env.

Thanks for the code again!