Graphical glitch when zooming

[Hombre]

I see an annoying graphical glitch when zooming : the image is first moved to its new top left position with the old image size, then a new image is computed.

Here is a patch that solve that. Could you please apply it ? (did not created a branch since it’s 3 lines of code)

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[agriggio]

crophandler: fixed glitch when zooming (thanks Hombre!)

Fixes #197

→ <<cset d9c193df8c4d>>