fixed an error with the column name "0".

[eisberg]

When reading a file with indexed column names: 0, 1, 2, ...

Get error:

In ParquetRowGroupReader.php line 100:
                                  
  '' does not exist in this file  

The error occurs because when defining the path, the array_filter function throws the normal value "0" equating it to NULL.

array_filter function without callback:

$entry = [
    0 => 'foo',
    1 => false,
    2 => -1,
    3 => null,
    4 => '',
    5 => '0',
    6 => 0,
];

print_r(array_filter($entry));

The above example will output:

Array
(
    [0] => foo
    [2] => -1
)