Initialize mle_fl_2d

Ensure mle_fl_2d(:,:) is set to 0.0 each time the subroutine
mixedlayer_restrat_OM4 is called. This prevents NaN values from
occurring.

src/parameterizations/lateral/MOM_mixed_layer_restrat.F90

@@ -277,7 +277,7 @@ subroutine mixedlayer_restrat_OM4(h, uhtr, vhtr, tv, forces, dt, h_MLD, VarMix,
   h_min = 0.5*GV%Angstrom_H ! This should be GV%Angstrom_H, but that value would change answers.
   covTS(:) = 0.0 !!Functionality not implemented yet; in future, should be passed in tv
   varS(:) = 0.0
-
+  mle_fl_2d(:,:) = 0.0
   vonKar_x_pi2 = CS%vonKar * 9.8696
 
   if (.not.associated(tv%eqn_of_state)) call MOM_error(FATAL, "mixedlayer_restrat_OM4: "// &