Set default values to crashing

Because variables in `grid_nml` should be all defined in the input file.

Overlap/eddy_graph.f90

@@ -28,7 +28,7 @@ program eddy_graph
   character(len = :), allocatable:: shpc_dir
   integer:: max_delta = 1
   
-  real:: corner_deg(2) = [0.125, - 59.875]
+  real:: corner_deg(2) = [huge(0.), huge(0.)]
   ! longitude and latitude of the corner of the whole grid in input
   ! NetCDF, in degrees
 
@@ -36,10 +36,12 @@ program eddy_graph
   ! longitude and latitude of the corner of the whole grid in input
   ! NetCDF, in rad
 
-  real:: step_deg(2) = [0.25, 0.25] ! longitude and latitude steps, in degrees
+  real:: step_deg(2) = [huge(0.), huge(0.)]
+  ! longitude and latitude steps, in degrees
+  
   real step(2) ! longitude and latitude steps, in rad
 
-  integer:: nlon = 120, nlat = 120
+  integer:: nlon = - 1, nlat = - 1
   ! size of ssh array in input NetCDF, assuming no repeated point if
   ! the grid is global