fix [#27096] Segmentation Fault trying to export DirectX with specific model

copying a mesh in editmode didnt NULL the edit_mesh pointer.

source/blender/blenkernel/intern/mesh.c

@@ -236,6 +236,8 @@ Mesh *copy_mesh(Mesh *me)
 	}
 	
 	men->mselect= NULL;
+	men->edit_mesh= NULL;
+	men->pv= NULL; /* looks like this is no-longer supported but NULL just incase */
 
 	men->bb= MEM_dupallocN(men->bb);
 	

source/blender/blenkernel/intern/particle.c

@@ -264,7 +264,6 @@ static void psys_create_frand(ParticleSystem *psys)
 int psys_check_enabled(Object *ob, ParticleSystem *psys)
 {
 	ParticleSystemModifierData *psmd;
-	Mesh *me;
 
 	if(psys->flag & PSYS_DISABLED || psys->flag & PSYS_DELETE || !psys->part)
 		return 0;