Make GDALAutoCreateWarpedVRT() return NULL when GDALSuggestedWarpOutput() fails; Test this fix and the one of the previous revision (related to GDALCreateGenImgProjTransformer2())

git-svn-id: https://svn.osgeo.org/gdal/trunk@26186 f0d54148-0727-0410-94bb-9a71ac55c965