--- a/mobile/android/components/SessionStore.js
+++ b/mobile/android/components/SessionStore.js
@@ -225,16 +225,18 @@ SessionStore.prototype = {
             type: "Tabs:TabsOpened"
           });
         }
         break;
       }
     }
   },
 
+  // Removal of line below tracked by bug 1360287
+  // eslint-disable-next-line complexity
   observe: function ss_observe(aSubject, aTopic, aData) {
     let observerService = Services.obs;
     switch (aTopic) {
       case "app-startup":
         EventDispatcher.instance.registerListener(this, [
           "ClosedTabs:StartNotifications",
           "ClosedTabs:StopNotifications",
           "Session:Restore",
@@ -399,19 +401,21 @@ SessionStore.prototype = {
         // Reset minimum interval between session store writes back to default.
         log("application-foreground");
         this._interval = Services.prefs.getIntPref("browser.sessionstore.interval");
         this._minSaveDelay = MINIMUM_SAVE_DELAY;
 
         // If we skipped restoring a zombified tab before backgrounding,
         // we might have to do it now instead.
         let window = Services.wm.getMostRecentWindow("navigator:browser");
-        if (window) { // Might not yet be ready during a cold startup.
+        if (window && window.BrowserApp) { // Might not yet be ready during a cold startup.
           let tab = window.BrowserApp.selectedTab;
-          this.restoreZombieTab(tab);
+          if (tab) { // Can be null if closing a tab triggered an activity switch.
+            this.restoreZombieTab(tab);
+          }
         }
         break;
       case "last-pb-context-exited":
         // Clear private closed tab data when we leave private browsing.
         for (let window of Object.values(this._windows)) {
           window.closedTabs = window.closedTabs.filter(tab => !tab.isPrivate);
         }
         this._lastClosedTabIndex = -1;