values smaller than 0.001 sat/B can't be represented by CFeeRate, but they are not rejected.

```
./src/bitcoin-cli -named sendtoaddress address=bcrt1qwkmhqum095zau5rf2velq55cq938vrd7uw8m4r amount=1.23 fee_rate=0.0009

error code: -6
error message:
Fee rate (0.000 sat/vB) is lower than the minimum fee rate setting (1.000 sat/vB)
```

```
./src/bitcoin-cli -named sendtoaddress address=bcrt1qwkmhqum095zau5rf2velq55cq938vrd7uw8m4r amount=1.23 fee_rate=0.000000000009

error code: -3
error message:
Invalid amount

{
    
    const std::unique_ptr<int> p_two = Assert(std::make_unique<int>(2));
    
    const int two = *Assert(p_two);
    Assert(two == 2);
    Assert(true);
    
    const bool result{Assume(two == 2)};
    Assert(result);
}
BOOST_AUTO_TEST_CASE(util_criticalsection)