Fix error reporting when config_nfglevels is insufficiently large

In init_atmosphere, during the interpolation of first-guess meteorological
fields from the intermediate files (config_init_case = 7 or 9), the value of
config_nfglevels must be set to a minimum of the number of vertical levels in
the intermediate file. Currently, the routines init_atm_case_gfs and
init_atm_case_lbc have a logic to throw an error and exit if config_nfglevels
is not sufficiently large. In practice, this error message is not reported
consistently with intermediate files containing many levels and/or many MPI
ranks being used.

This commit fixes the inconsistent error reporting issue by adding the required
deallocate statements before the repeated calls to read_next_met_field in the
case of config_nfglevels being insufficiently large. Without the deallocate,
one or more MPI ranks crash during the read of the field % slab from the
intermediate file. This typically results in a crash of init_atmosphere without
any useful error messages in the log files.

Author: abishekg7

src/core_init_atmosphere/mpas_init_atm_cases.F

@@ -3547,6 +3547,7 @@ subroutine init_atm_case_gfs(block, mesh, nCells, nEdges, nVertLevels, fg, state
                ! many unique levels are found using the code above
                !
                if (too_many_fg_levs) then
+                  deallocate(field % slab)
                   call read_next_met_field(field, istatus)
                   cycle
                end if
@@ -5283,6 +5284,7 @@ subroutine init_atm_case_lbc(timestamp, block, mesh, nCells, nEdges, nVertLevels
                ! many unique levels are found using the code above
                !
                if (too_many_fg_levs) then
+                  deallocate(field % slab)
                   call read_next_met_field(field, istatus)
                   cycle
                end if