Fix "No Session" in plugin messaging

After Bungee recieved a plugin message from Bukkit, that it has
completed login/register for a Floodgate player, bungee would throw a
NullPointerException: Cannot invoke "BungeeLoginSession.getProfile()"
because "loginSession" is null

bungee/src/main/java/com/github/games647/fastlogin/bungee/task/FloodgateAuthTask.java

@@ -53,6 +53,7 @@ public class FloodgateAuthTask
     @Override
     protected void startLogin() {
         BungeeLoginSession session = new BungeeLoginSession(player.getName(), isRegistered, profile);
+        core.getPlugin().getSession().put(player.getPendingConnection(), session);
 
         // enable auto login based on the value of 'autoLoginFloodgate' in config.yml
         boolean forcedOnlineMode = autoLoginFloodgate.equals("true")