Add-on Signature Check cannot be disabled in Abrowser.

Mozilla Firefox 40.0 issues a warning when unsigned add-on/extension other than those from http://addons.mozilla.org/ are encountered.

Abrowser 40.0 is forked from Mozilla Firefox 40.0; Naturally modified/added add-ons like AbrowserHome and Private Browsing Tor Proxy are flagged as unverified for the current version. (See the attachment.)

One way, to disable the add-on signature check is;

[1] Type about:config in the location/address bar of Abrowser and press enter key. It'll open the configuration editor.
[2] Now type xpinstall in Search filter box and it'll show a few results in the window.
[3] Double-click on xpinstall.signatures.required preference and it'll change its value to false.

But for Abrowser, the default value for xpinstall.signatures.required is false; Yet the warning is not getting removed.

Is there some other settings that needs to be changed?

Hope the later Abrowser versions will be released after disabling the add-on signature check imposed by Mozilla.