NaN values in SNAP toolbox

[mengdahl]

@marpet please check this issue too, it’s bothering some users:

GPT results in no-data value of 0 instead of NaN pixels

So, no suggestions? Someone put this thread under s1tbx, which I think is a pity since it is a general SNAP issue I face; no data in SNAP becomes 0 in an exported image, no matter the format.