**Describe the bug**
When you set the setting `input_format_with_names_use_header` to `0`, `INSERT` does not actually insert rows.

**How to reproduce**
* Which ClickHouse server version to use: git master `a21fe0b492cbc8628126a3cd493b83e82abf9978`, checked out on 2021-03-31
* Which interface to use: the native command-line client
* Non-default settings, if any: `input_format_with_names_use_header` = `0`
* `CREATE TABLE` statements for all tables involved:
```sql
CREATE TABLE csvtest
(
    `t` String
)
ENGINE = MergeTree
ORDER BY t
```
* Sample data for all these tables
`test.csv`:
```csv
t
testdata1
testdata2
```
* Queries to run that lead to unexpected result:
```
% clickhouse-client --input_format_with_names_use_header 0 --query "INSERT INTO csvtest FORMAT CSVWithNames" < test.csv
```

**Expected behavior**
Two rows `('testdata1'), ('testdata2')` will be inserted to the table `csvtest`.

**Error message and/or stacktrace**
Nothing. It silently discards the input and inserts nothing to the table.

**Additional context**
It works as expected if you set `input_format_with_names_use_header` to `1`.

bool with_names_, const FormatSettings & format_settings_)
    : RowInputFormatWithDiagnosticInfo(header_, in_, params_)
    , with_names(with_names_)
    , format_settings(format_settings_)
{
    const String bad_delimiters = " \t\"'.UL";
    if (bad_delimiters.find(format_settings.csv.delimiter) != String::npos)
        throw Exception(String("CSV format may not work correctly with delimiter '") + format_settings.csv.delimiter +
                        "'. Try use CustomSeparated format instead.", ErrorCodes::BAD_ARGUMENTS);
    const auto & sample = getPort().getHeader();
    size_t num_columns = sample.columns();
    data_types.resize(num_columns);
    column_indexes_by_names.reserve(num_columns);
    for (size_t i = 0; i < num_columns; ++i)
    {
        const auto & column_info = sample.getByPosition(i);
        data_types[i] = column_info.type;
        column_indexes_by_names.emplace(column_info.name, i);
    }
}
void CSVRowInputFormat::addInputColumn(const String & column_name)