NeuralStyleTransfer example

[RobAltena]

Issue Description

Different from #857 . The NeuralStyleTransfer example crashes here.

Exception in thread "main" java.lang.IllegalStateException: Cannot perform backprop: Dropout mask array is absent (already cleared?)

Version Information

Win10, beta5, cpu.

[saudet]

/cc @AlexDBlack

[carlosorrego]

i get the same error

[eraly]

@carlosorrego For now as a workaround you can set the IDropout to null before this line. There isn't any dropout in the net here. Looks like the forward pass somehow doesn't set the mask arrays to one. Not sure why there are even mask arrays here in the first place...

            layer.conf().getLayer().setIDropout(null);

[carlosorrego]

@eraly thanks very much Susan. Really appreciated.