### gcd on polynomials over ZZ

In Sage 9.4, in the following code:

```
P.<x> = QQ[]
pol = 2*x^2 + 4*x + 6
print( gcd(pol) )
print( gcd(pol.change_ring(ZZ)) )
```

The first `gcd`

works fine, while the second `gcd`

results in

`TypeError: object of type 'sage.rings.polynomial.polynomial_integer_dense_flint.Polynomial_integer_dense_flint' has no len()`

There is a workaround by using `gcd(pol.coefficients())`

, but I wonder if above error is a bug.