fix Python new_from_array()
fix Python new_from_array()

under some circumstances it could modify the passed-in array, now it
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lovell/libvips,leiyangyou/libvips,leiyangyou/libvips,jcupitt/libvips,jcupitt/libvips,leiyangyou/libvips,mcanthony/libvips,leiyangyou/libvips,lovell/libvips,mcanthony/libvips,jcupitt/libvips,mcanthony/libvips,lovell/libvips,mcanthony/libvips,lovell/libvips,jcupitt/libvips