Improved Conditional Logic Handling in Email Builder

**Issue with Conditional Elements**: Conditional elements did not evaluate correctly when custom fields were either empty or undefined, leading to silent failures.

• Enhanced the comparator function used in conditional logic to properly manage undefined, null, and empty string values.
• Conditional logic will now operate as expected, even when custom fields for a contact have not been set.

• Ensures conditions render accurately, regardless of field status
• Removes silent failures in email logic
• Enhances the reliability of personalised and dynamic content