98043d3fc3
Blender crashes when a File Output was created when the Use Preview
option of the render output settings was enabled. This is a regression
introduced in 931c188ce5, where the image format of the node was
initialized from the scene image settings, so the preview option was
carried over, yet it is not supported nor exposed to the user in the
File Output node. To fix this, ensure the file output code will ignore
previews.