Raise error when training xception+deeplabv3p with SGD

[zhudaoruyi]

tensorflow.python.framework.errors_impl.InvalidArgumentError: Reshape cannot infer the missing input size for an empty tensor unless all specified input sizes are non-zero
         [[Node: training/SGD/gradients/loss/activation_82_loss/descending_sort_0_grad/Reshape = Reshape[T=DT_INT32, Tshape=DT_INT32, _class=["loc:@train...rseToDense"], _device="/job:localhost/replica:0/task:0/device:CPU:0"](loss/activation_82_loss/descending_sort_0:1, training/SGD/gradients/loss/activation_82_loss/descending_sort_0_grad/stack)]]

Raise error with LovaszSoftmax and no error with jaccard loss or others, where I keep the same datasets,networks,optimizers and params.