FIX: false overrides should be permitted via ENV

lib/site_setting_extension.rb

@@ -121,7 +121,7 @@ module SiteSettingExtension
       # exists it will be used instead of the setting and the setting will be hidden.
       # Useful for things like API keys on multisite.
       if opts[:shadowed_by_global] && GlobalSetting.respond_to?(name)
-        if (val = GlobalSetting.send(name)).present?
+        unless (val = GlobalSetting.send(name)) == ''.freeze
           hidden_settings << name
           shadowed_settings << name
           current_value = val

spec/components/site_setting_extension_spec.rb

@@ -470,6 +470,18 @@ describe SiteSettingExtension do
       end
     end
 
+    context "with a false override" do
+      before do
+        GlobalSetting.stubs(:bool).returns(false)
+        settings.setting(:bool, true, shadowed_by_global: true)
+        settings.refresh!
+      end
+
+      it "should return default cause nothing is set" do
+        expect(settings.bool).to eq(false)
+      end
+    end
+
     context "with global setting" do
       before do
         GlobalSetting.stubs(:trout_api_key).returns('purringcat')