Do not replace sprite mode if no change to Backpack inventory

Which should hopefully fix compatibility issues with Jungle Helper's lantern, since it is based on sprite mode

Triggers/SetCustomInventoryTrigger.cs

@@ -4,10 +4,10 @@
 namespace Celeste.Mod.MaxHelpingHand.Triggers {
     [CustomEntity("MaxHelpingHand/SetCustomInventoryTrigger")]
     public class SetCustomInventoryTrigger : Trigger {
-        private int dashes = 1;
-        private bool dreamDash = false;
-        private bool groundRefills = true;
-        private bool backpack = true;
+        private readonly int dashes;
+        private readonly bool dreamDash;
+        private readonly bool groundRefills;
+        private readonly bool backpack;
 
         public SetCustomInventoryTrigger(EntityData data, Vector2 offset) : base(data, offset) {
             dashes = data.Int("dashes");
@@ -17,9 +17,12 @@ public SetCustomInventoryTrigger(EntityData data, Vector2 offset) : base(data, o
         }
 
         public override void OnEnter(Player player) {
-            (Scene as Level).Session.Inventory = new PlayerInventory(dashes, dreamDash, backpack, !groundRefills);
+            Session session = (Scene as Level).Session;
+            bool hadBackpack = session.Inventory.Backpack;
 
-            if (!SaveData.Instance.Assists.PlayAsBadeline) {
+            session.Inventory = new PlayerInventory(dashes, dreamDash, backpack, !groundRefills);
+
+            if (!SaveData.Instance.Assists.PlayAsBadeline && hadBackpack != backpack) {
                 player.ResetSprite(backpack ? PlayerSpriteMode.Madeline : PlayerSpriteMode.MadelineNoBackpack);
             }
         }