manualUpdateAssetFetchPeriod=0 is ignored

[mikhaelkh]

Describe the issue

When manualUpdateAssetFetchPeriod is set 0, it seems that the value is ignored and assumed the default 2000, but I think in this case user tries to tell uBO that he wants to set the delay as little as possible and this case should be parsed accordingly.

Steps for anyone to reproduce the issue

1. Set manualUpdateAssetFetchPeriod to 0
2. Click Purge all caches & Update now
3. Update is significantly slower than with manualUpdateAssetFetchPeriod set to 1.

Your settings

[If you fail to provide this info, I will mark the issue as invalid. Lists all settings which differs from default settings]

• OS/version: Windows 10 v1607 x64
• Browser/version: Chrome
• uBlock Origin version: latest dev from Store (1.14.23.2)

Your filter lists

  "selectedFilterLists": [
    "https://filters.adtidy.org/extension/ublock/filters/4.txt",
    "https://easylist-downloads.adblockplus.org/cntblock.txt",
    "https://easylist-downloads.adblockplus.org/bitblock.txt",
    "https://raw.githubusercontent.com/hoshsadiq/adblock-nocoin-list/master/nocoin.txt",
    "https://raw.githubusercontent.com/jspenguin2017/uBlockProtector/master/uBlockProtectorList.txt",
    "https://raw.githubusercontent.com/StevenBlack/hosts/master/hosts",
    "RUS-0",
    "hphosts",
    "fanboy-thirdparty_social",
    "fanboy-annoyance",
    "spam404-0",
    "malware-1",
    "disconnect-malvertising",
    "fanboy-enhanced",
    "easyprivacy",
    "adguard-spyware",
    "easylist",
    "adguard-generic",
    "awrl-0",
    "ublock-unbreak",
    "ublock-abuse",
    "ublock-privacy",
    "ublock-experimental",
    "ublock-badware",
    "ublock-annoyances",
    "ublock-filters",
    "user-filters"
  ],

[Atavic]

I think the lowest value is actually 1 while 0 is not valid there.

[jspenguin2017]

In messaging.js:

    case 'forceUpdateAssets':
        µb.scheduleAssetUpdater(0);
        µb.assets.updateStart({ delay: µb.hiddenSettings.manualUpdateAssetFetchPeriod || 500 });
        break;

Maybe try -1? Negative value passed to setTimeout will be automatically changed to 0.