gf_getfld() leaks memory on error

[edwardhartnett]

In gf_getfld() we have:

!         If found Section 1, decode elements in Identification Section.
          if (isecnum.eq.1) then
              iofst = iofst-40    ! reset offset to beginning of section
              call gf_unpack1(cgrib, lcgrib, iofst, gfld%idsect,
     &             gfld%idsectlen, jerr)
              if (jerr.ne.0) then
                  ierr = 15
                  return
              endif
          endif

!         If found Section 2, Grab local section. Save in case this is
!         the latest one before the requested field.
          if (isecnum.eq.2) then
              iofst = iofst-40    ! reset offset to beginning of section
              if (associated(gfld%local)) deallocate(gfld%local)
              call gf_unpack2(cgrib, lcgrib, iofst, gfld%locallen,
     &             gfld%local, jerr)
              if (jerr.ne.0) then
                  ierr = 16
                  return
              endif
          endif

The gf_unpack1() function allocates an array in gfld. If the function later exits, this memory is not freed and causes a leak.

The solution is to call gf_free() on gfld before an error exit.

There are a bunch of currently commented-out tests that demonstrate this bug in test_getfield.f90.