Small fix

Signed-off-by: Nicola Vigano <nicola.vigano@esrf.fr>

zUtil_Deformation/gtDefSyntheticGrainCreate.m

@@ -194,7 +194,7 @@ disp(min(dmvol(:)))
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
 % Cleaning grain struct
-if (isfield(grain, 'id'))
+if (~isfield(grain, 'id') || isempty(grain.id))
     grain.id = 1;
 end
 grain = struct('id', grain.id, 'phaseid', grain.phaseid, ...