PHN Number Not Generated Correctly When Clicking Generate Button

[Irani96]

File Path: /opd/patient_edit.xhtml

Description:
The Generate PHN button is not functioning correctly. When clicked, a new PHN number is not generated. Additionally, if a PHN number has already been generated, clicking the Generate button removes the existing PHN number instead of retaining or regenerating it.

Steps to Reproduce:

1. Open the patient registration/admission screen
2. Click the Generate PHN button
3. Observe the PHN number field
4. If a PHN already exists, click Generate PHN again

Actual Result:

PHN number is not generated when clicking the Generate button
Existing PHN number is removed when the Generate button is clicked again

Expected Behavior:

A unique PHN number should be generated when clicking the Generate button
If a PHN number already exists, it should not be removed unintentionally