Bug fix: define `timings_file` after reading slice

The bug comes from commit 1cfed454.

Inst_eddies/inst_eddies.f90

@@ -69,6 +69,9 @@ program inst_eddies
 
   call assert(IEEE_SUPPORT_DATATYPE(0.), ieee_support_nan(0.), &
        "inst_eddies: not enough IEEE support")
+  call cpu_time(t0)
+  print *, "inst_eddies: Enter dates_nml:"
+  read(unit = *, nml = dates_nml)
   write(timings_file, fmt = '("SHPC/Slice_", i0, "/timings.txt")') slice
   inquire(file = timings_file, exist = exist)
   call new_unit(unit)
@@ -80,9 +83,6 @@ program inst_eddies
      OPEN(unit, file = timings_file, STATUS = "new", ACTION = "WRITE")
   end if
 
-  call cpu_time(t0)
-  print *, "inst_eddies: Enter dates_nml:"
-  read(unit = *, nml = dates_nml)
   call config
   call input_ssh(corner, step, nlon, nlat, periodic, ssh, u, v)