NOAA-GFDL/FMS

AI Summary: The task is to debug and fix a bug in the FMS (Flexible Modeling System) code. The bug occurs in the `grid2_init` function, where the absence of a `grid_spec.nc` file leads to undefined behavior in subsequent function calls like `get_grid_ntiles`. The solution involves modifying `grid2_init` and related functions to handle the missing file gracefully, potentially by raising an error or ensuring proper initialization before proceeding. This requires understanding Fortran 90 code and the FMS framework.