Bug 1594083 - Check if we got the pref service before using it to avoid a crash r=mhowell

Differential Revision: https://phabricator.services.mozilla.com/D59016

--HG--
extra : moz-landing-system : lando

toolkit/components/fuzzyfox/Fuzzyfox.cpp

@@ -72,8 +72,14 @@ Fuzzyfox::Fuzzyfox()
 
   sFuzzyfoxInitializing = fuzzyfoxEnabled;
 
-  // Should I see if these fail? And do what?
   nsCOMPtr<nsIPrefBranch> prefs = do_GetService(NS_PREFSERVICE_CONTRACTID);
+  if (!prefs) {
+    // Sometimes the call to the pref service fails. If that happens, we
+    // don't add the observers. The user will have to restart to have
+    // preference changes take effect.
+    return;
+  }
+
   prefs->AddObserver(FUZZYFOX_ENABLED_PREF, this, false);
   prefs->AddObserver(FUZZYFOX_CLOCKGRAIN_PREF, this, false);
 }