clarify the comment on the out-of-bounds check from #723

lapack/getf2/zgetf2_k.c

@@ -99,7 +99,7 @@ blasint CNAME(blas_arg_t *args, BLASLONG *range_m, BLASLONG *range_n, FLOAT *sa,
       GEMV_N(m - j, j, 0, dm1,  ZERO, a + j * 2, lda, b, 1, b + j * 2, 1, sb);
 
       jp = j + IAMAX_K(m - j, b + j * 2, 1);
-      if (jp>m) jp = m;        //avoid out of boundary
+      if (jp>m) jp = m;        //avoid out of boundary when the iamax kernel does not cope with NaN in input, see gh issue 723
       ipiv[j + offset] = jp + offset;
       jp--;