Update TTD initial state

TTD initial state was 0, which was not allowing the TTD ticker to actually start. This changes a unit's ttd_ticker to initialize as false

src/Unit/Unit.lua

@@ -13,7 +13,7 @@ local Unit = {
     last_off_attack = 0,
     last_main_attack = 0,
     last_combat_time = 0,
-    ttd_ticker = 0,
+    ttd_ticker = false,
     ttd = 0,
     id = false,
 }