Core/Unit: Fix units on vehicles not dismounting on death (#25404)

* Core/Unit: Fix units on vehicles not dismounting on death

Closes #23095
Issue added in 982643cd96790ffc54e7a3e507469649f3b074d2

* Remove leftovers from previous tries

(cherry picked from commit ff26027453179448bb972d88a51e565d71e95f3f)

src/server/game/Entities/Unit/Unit.cpp

@@ -8216,6 +8216,8 @@ void Unit::setDeathState(DeathState s)
     // Death state needs to be updated before RemoveAllAurasOnDeath() is called, to prevent entering combat
     m_deathState = s;
 
+    bool isOnVehicle = GetVehicle() != nullptr;
+
     if (s != ALIVE && s != JUST_RESPAWNED)
     {
         CombatStop();
@@ -8236,18 +8238,25 @@ void Unit::setDeathState(DeathState s)
         // remove aurastates allowing special moves
         ClearAllReactives();
         ClearDiminishings();
-        if (IsInWorld())
+
+        // Don't clear the movement if the Unit was on a vehicle as we are exiting now
+        if (!isOnVehicle)
         {
-            // Only clear MotionMaster for entities that exists in world
-            // Avoids crashes in the following conditions :
-            //  * Using 'call pet' on dead pets
-            //  * Using 'call stabled pet'
-            //  * Logging in with dead pets
-            GetMotionMaster()->Clear();
-            GetMotionMaster()->MoveIdle();
+            if (IsInWorld())
+            {
+                // Only clear MotionMaster for entities that exists in world
+                // Avoids crashes in the following conditions :
+                //  * Using 'call pet' on dead pets
+                //  * Using 'call stabled pet'
+                //  * Logging in with dead pets
+                GetMotionMaster()->Clear();
+                GetMotionMaster()->MoveIdle();
+            }
+
+            StopMoving();
+            DisableSpline();
         }
-        StopMoving();
-        DisableSpline();
+
         // without this when removing IncreaseMaxHealth aura player may stuck with 1 hp
         // do not why since in IncreaseMaxHealth currenthealth is checked
         SetHealth(0);