In the file p12_key.c, the function PKCS12_key_gen_uni has the following code:

u = EVP_MD_size(md_type);
if (u < 0 || v <= 0)
    goto err;
...
for (j = 0; j < v; j++)
    B[j] = Ai[j % u];

The variable u is used as a divisor. Since the code explicitly checks whether u is negative, I think it should also avoid the case when u=0 to prevent divide by zero bugs.