This PR fixes a potential issue when a user clicks "Save" from the web UI and can null out empty array fields or even change types (ie: Array to String).

In my case I had only a single mac_scan_blacklist value, the mac address of the Bjorn device itself. When the UI presented this value xx:xx:xx:xx it did not include a , character and was being skipped by the check value.includes(',') in config.js.

The code now tracks known array fields and will either test if the value includes a , or if the form field is a known array type. This will allow the array based form fields to hit the same logic path and keep the data type accurate and consistent.

I could verify this change by grepping the shared_config.json and watching the "Save" turn the config into this:

 cat ../../config/shared_config.json | grep "blacklist"
    "blacklistcheck": true,
    "mac_scan_blacklist": "xx:xx:xx:xx:xx:d8",
    "ip_scan_blacklist": "null",

Then after the code fix

cat ../../config/shared_config.json | grep "blacklist" -A3
    "blacklistcheck": true,
    "displaying_csv": true,
    "log_debug": true,
    "log_info": true,
--
    "mac_scan_blacklist": [
        "xx:xx:xx:xx:xx:d8"
    ],
    "ip_scan_blacklist": [
        "null"
    ],
    "steal_file_names": [