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I'm not sure that I see any white line in your image.

I have not worked in Corel products for years but I am going to guess that any white lines might be caused by exporting an image that is not in exact pixel amounts (for example, 467.7 pixels vs 467 pixels).

If your width is in fractional pixel amounts, the program anti-aliases the edge to blend with the background and this can cause a fringe or lighter colored outline.