Fix PHP 8.4 ValueError when str_getcsv() receives empty enclosure

[richardlhr]

Summary

Fixes a PHP 8+ compatibility issue in SendPress_Data::csv_to_array().

When csv_to_array() is called without an enclosure argument, the default value is an empty string:

$enclosure = '';

This value is then passed directly to:

str_getcsv($csv_line, $delimiter, $enclosure);

PHP 8+ now throws:

ValueError: str_getcsv(): Argument #3 ($enclosure) must be a single character

because the enclosure parameter must contain exactly one character.

Fix

Use the standard CSV enclosure character (") when no enclosure is provided.

This restores compatibility with PHP 8.x while preserving existing behavior.

Tested

• PHP 8.1
• PHP 8.2
• PHP 8.3
• PHP 8.4