Minor correction for AVX512. Don't access vector of mask struct.

src/runner_doiact_vec.c

@@ -745,7 +745,7 @@ __attribute__((always_inline)) INLINE void runner_doself2_force_vec(
       vec_create_mask(v_doi_mask, vec_cmp_lt(v_r2.v, v_h2.v));
 
       /* Combine all 3 masks and form integer mask. */
-      v_doi_mask.v = vec_mask_and(v_doi_mask, v_doi_mask_self_check);
+      v_doi_mask = vec_mask_and(v_doi_mask, v_doi_mask_self_check);
       doi_mask = vec_form_int_mask(v_doi_mask);
 
       /* If there are any interactions perform them. */