update handling of Lua assets

Editor/LuaFileAssetEditor.cs

@@ -5,11 +5,11 @@ using UnityEngine;
 [CustomEditor(typeof(LuaFile))]
 public class LuaScriptAssetEditor : Editor
 {
+    private TextAsset asset;
+
     public override void OnInspectorGUI()
     {
         LuaFile luaScriptAsset = (LuaFile)target;
-        
-        // Allow user to drag-and-drop the Lua file
-        luaScriptAsset.luaScript = (TextAsset)EditorGUILayout.ObjectField("Lua Script", luaScriptAsset.luaScript, typeof(TextAsset), false);
+        EditorGUILayout.TextArea(luaScriptAsset.LuaScript);
     }
 }