Bug 1283067 - followup, rs=obvious-oversight

MozReview-Commit-ID: 4aosVpyiOFO

browser/modules/WindowsPreviewPerTab.jsm

@@ -452,7 +452,6 @@ TabWindow.prototype = {
     preview.active = this.tabbrowser.selectedTab == controller.tab;
     // Grab the default favicon
     getFaviconAsImage(
-      null,
       null,
       PrivateBrowsingUtils.isWindowPrivate(this.win),
       function (img) {