```
clickhouse-client -q 'create table typed_nulls( str Nullable(String) ) Engine=Log'

clickhouse-client --param_n='\N' --query='insert into typed_nulls(str) values ( {n:Nullable(String)} )' --format=Vertical
Code: 456. DB::Exception: Query parameter `n` was not set

clickhouse-client --param_n='aa' --query='insert into typed_nulls(str) values ( {n:Nullable(String)} )' --format=Vertical
Code: 456. DB::Exception: Query parameter `n` was not set
```

See also https://github.com/ClickHouse/ClickHouse/commit/a58996817ff0f639686f4248ac0be43a000aac85
/cc @tavplubix 
{
    for (auto & child : ast->children)
    {
        if (child->as<ASTQueryParameter>())
            visitQueryParameter(child);
        else
            visit(child);
    }
}
const String & ReplaceQueryParameterVisitor::getParamValue(const String & name)