Fix privacyDropdown is null issue

[luochen1990]

The issue:

Uncaught TypeError: Cannot read properties of null (reading 'value')
    at fileOversized ((index):239:33)
    at HTMLInputElement.<anonymous> ((index):284:9)

Related JS code:

159    const privacyDropdown = document.getElementById("privacy");

239            if (privacyDropdown.value == "secret") {