Fix cropping when exporting about darktable HOT 3 OPEN

1. There are already some reports here about export size and cropping, are you sure this is different?
2. The tooltips tell for the size in pixels something like "maximum limit", if you just define the height as 1020 and leave the width at 0 should give exported file always the defined height. Does this give inconsistant sizes?

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I have tried to leave the width to 1020, but no change, the result is still 1019. I can provide the .NEF if you want, no problem. From what I can see searching the issue, this is not a duplicate. Thx

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Can reproduce, depends on provided size - either by crop iop or provided data from raw or after rawprepare tuning.

1. not sure how to fix ...
2. basically a duplicate of #16638, it's all the same story and we have had more reports before.

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