Fix missing reference to GroupTools in ReadyCheckManager

diff --git a/ReadyCheckManager.lua b/ReadyCheckManager.lua
index a5aa99a..6fb727d 100644
--- a/ReadyCheckManager.lua
+++ b/ReadyCheckManager.lua
@@ -34,6 +34,7 @@ C.ReadyCheckManager = {}

 local L = C.LocaleManager
 local RCM = C.ReadyCheckManager
+local GT = C.GroupTools
 local CM

 local MAX_DELAY = 55