error in deriving transform from corner coords

[mdsumner]

when there's no transform on the json, it means it is the default transform:

0 1 0 0 0 1

so this is a mistake:

https://github.com/hypertidy/vapour/blob/5e67be7626051b3f444b7fec49d829cf3ab6444c/R/raster-info.R#L166

The cornerCoordinates in this case sit in 0,ncol, nrow, 0 - i.e. upside down, and at least the json reflects the fact that the geotransform was not set.