short vectors throws an inexact error for some unreasonably big inputs

So we don't forget about it. 
```
julia> L = integer_lattice(gram=ZZ[2;])
Integer lattice of rank 1 and degree 1
with gram matrix
[2]

julia> short_vectors(L,ZZ(324280870480906391479841483778926003675359966482821906547016802))
ERROR: InexactError: convert(Int64, 12733437683534372083542052402953)
```
... but then probably no one wants the $10^{31}$ long list of outputs here. 