grdinfo fails to report z_min/max when z var has no *actual_range* attribute #6765
Description
It was brought to my attention today by Christian Ferreira from MB that grdinfo fails to report the z min/max values. It turns out that that the grids in question have no actual_range but oddly the report is that v_min and v_max are zero. Not z_min, z_max.
Example grid can be downloaded from here
So shamelessly GEBCO is not setting the actual_range attribute and calls elevation to the z array. But this is a grdinfo regression, I think.
grdinfo gebco_2021_n35.50506591796875_s31.96197509765625_w22.9449462890625_e27.2021484375.nc
gebco_2021_n35.50506591796875_s31.96197509765625_w22.9449462890625_e27.2021484375.nc: Title: The GEBCO_2021 Grid - a continuous terrain model for oceans and land at 15 arc-second intervals
gebco_2021_n35.50506591796875_s31.96197509765625_w22.9449462890625_e27.2021484375.nc: Command: Information on the development of the data set and the source data sets included in the grid can be found in the data set documentation available from https://www.gebco.net
gebco_2021_n35.50506591796875_s31.96197509765625_w22.9449462890625_e27.2021484375.nc: Remark:
gebco_2021_n35.50506591796875_s31.96197509765625_w22.9449462890625_e27.2021484375.nc: Pixel node registration used [Geographic grid]
gebco_2021_n35.50506591796875_s31.96197509765625_w22.9449462890625_e27.2021484375.nc: Grid file format: ns = GMT netCDF format (16-bit integer), CF-1.7
gebco_2021_n35.50506591796875_s31.96197509765625_w22.9449462890625_e27.2021484375.nc: x_min: 22.9458333333 x_max: 27.2041666667 x_inc: 0.00416666666667 (15 sec) name: longitude n_columns: 1022
gebco_2021_n35.50506591796875_s31.96197509765625_w22.9449462890625_e27.2021484375.nc: y_min: 31.9625 y_max: 35.5041666667 y_inc: 0.00416666666667 (15 sec) name: latitude n_rows: 850
gebco_2021_n35.50506591796875_s31.96197509765625_w22.9449462890625_e27.2021484375.nc: v_min: 0 v_max: 0 name: Elevation relative to sea level [m]
gebco_2021_n35.50506591796875_s31.96197509765625_w22.9449462890625_e27.2021484375.nc: scale_factor: 1 add_offset: 0
gebco_2021_n35.50506591796875_s31.96197509765625_w22.9449462890625_e27.2021484375.nc: format: classic
gebco_2021_n35.50506591796875_s31.96197509765625_w22.9449462890625_e27.2021484375.nc: Default CPT: