**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`.

skipWhitespacesAndTabs(in);
        }
        else
        {
            
            String tmp;
            readCSVString(tmp, in, format_settings.csv);
        }
        skipDelimiter(in, delimiter, is_last_file_column);
    }
    if (have_default_columns)
    {
        for (size_t i = 0; i < column_mapping->read_columns.size(); i++)
        {
            if (!column_mapping->read_columns[i])
            {
                
                
                
                
                
                
                columns[i]->insertDefault();
                ext.read_columns[i] = false;
            }
        }
    }
    return true;
}
bool CSVRowInputFormat::parseRowAndPrintDiagnosticInfo(MutableColumns & columns, WriteBuffer & out)