fix: Fix segmentation fault caused by double-free of field_name

[matapatos]

Summary

• Fixed segmentation fault in integration tests caused by double-free of field_name string
• The issue was introduced in commit 7325936 which moved zend_string_release earlier but kept the release at loop end

Root Cause

When processing model properties in the validate function:

• If field_value != NULL (field exists or has default value)
• And is_to_release_field_name is true (field_name was allocated due to Alias attribute or aliasGenerator)
• And valid_value != NULL (validation succeeded)

The field_name would be released twice:

1. At the early release point (line 188 in old code)
2. At the end of the loop (line 208 in old code)

This double-free causes undefined behavior and segmentation faults.

Solution

1. Removed the problematic early release that was causing the double-free
2. Added proper releases at all exception/return paths to prevent memory leaks
3. Moved is_to_release_field_name calculation before exception checks for consistency
4. Initialized field_name to NULL to avoid potential undefined behavior

Verification

All code paths now release field_name exactly once:

• When get_property_name throws exception
• When field_value is NULL and stop_first_error is true
• When field_value is NULL and stop_first_error is false
• When validate_field_value throws exception
• When valid_value is NULL and stop_first_error is false
• When valid_value is NULL and stop_first_error is true
• When validation succeeds