Throw error with seth 4byte if no matching signatures

right now if you search up a 4byte sig with no matches the command just succeeds but returns nothing:

```
❯ seth 4byte 0xd0a164fb
```

can see why with verbose:

```
❯ seth 4byte 0xd0a164fb -v
{
"count": 0,
"next": null,
"previous": null,
"results": []
}
```

it should show an error message and exit with an error code like `1` if no results are found instead