Fix unit tests which were unintentionally broke with recent changes

- site utils test breaking caused with brave#7207. Was always adding location, even when not present (which is the case for folders)
- preferences needed SVG stub after adding new icon with brave#7157

Auditors: @darkdh, @cezaraugusto

Test Plan:
npm run unittest

js/state/siteUtil.js

@@ -254,7 +254,9 @@ module.exports.addSite = function (sites, siteDetail, tag, originalSiteDetail, s
     sites = sites.delete(oldKey)
   }
 
-  site = site.set('location', UrlUtil.getLocationIfPDF(site.get('location')))
+  if (site.has('location')) {
+    site = site.set('location', UrlUtil.getLocationIfPDF(site.get('location')))
+  }
 
   const key = module.exports.getSiteKey(site)
   if (key === null) {

test/unit/about/preferencesTest.js

@@ -24,6 +24,7 @@ describe('Preferences component', function () {
     mockery.registerMock('../../less/button.less', {})
     mockery.registerMock('../../node_modules/font-awesome/css/font-awesome.css', {})
     mockery.registerMock('../../extensions/brave/img/caret_down_grey.svg', 'caret_down_grey.svg')
+    mockery.registerMock('../../app/extensions/brave/img/preferences/browser_prefs_plugins.svg', 'browser_prefs_plugins.svg')
     window.chrome = fakeElectron
     window.CustomEvent = {}