Core/Movement: Improve log when starting a spline with invalid arguments

Improve log when starting a spline with invalid arguments, for example when starting a spline with just 1 point.

src/server/game/Movement/Spline/MoveSpline.cpp

@@ -212,7 +212,7 @@ bool MoveSplineInitArgs::Validate(Unit* unit) const
     if (!(exp))\
     {\
         if (unit)\
-            TC_LOG_ERROR("misc.movesplineinitargs", "MoveSplineInitArgs::Validate: expression '%s' failed for GUID: %u Entry: %u", #exp, unit->GetTypeId() == TYPEID_PLAYER ? unit->GetGUID().GetCounter() : unit->ToCreature()->GetSpawnId(), unit->GetEntry());\
+            TC_LOG_ERROR("misc.movesplineinitargs", "MoveSplineInitArgs::Validate: expression '%s' failed for %s", #exp, unit->GetDebugInfo().c_str());\
         else\
             TC_LOG_ERROR("misc.movesplineinitargs", "MoveSplineInitArgs::Validate: expression '%s' failed for cyclic spline continuation", #exp); \
         return false;\