Prevent race condition

app/src/main/java/eu/faircode/email/ServiceSynchronize.java

@@ -1331,6 +1331,8 @@ public class ServiceSynchronize extends ServiceBase implements SharedPreferences
                 db.account().setAccountBackoff(account.id, null);
             while (state.isRunning() && currentThread.equals(accountThread)) {
                 state.reset();
+                if (!state.isRunning())
+                    break;
                 Log.i(account.name + " run thread=" + currentThread);
 
                 final ObjectHolder<TwoStateOwner> cowner = new ObjectHolder<>();