Windows 8.1, Nvidia GTX 760 M
Broken: 2.79 5bd8ac9
Short description of error
Using Filter node as Image input to Scale node and Texture node as input to X and Y offsets of Scale node renders empty image.
Exact steps for others to reproduce the error
Switch to Compositing
Add Texture node with Clouds texture
Add Filter Node with Sobel on
Add Scale Node with Relative on
Add Viewer node
Connect Images of Texture To Sobel To Scale To Viewer
Connect Texture Color output to X input of Scale node
After that in my case - the Backdrop is empty. Viewer Node in Image Editor is transparent or black if disabled Use Alpha.
File with the node setup: