Update Treeview.lua

Author: NoryiE

Basalt/objects/Treeview.lua

@@ -91,9 +91,9 @@ return function(name, basalt)
                     onSelect(node)
                 end
             end,
-
-            setExpandable = function(self, expandable)
-                expandable = expandable
+            
+            setExpandable = function(self, _expandable)
+                expandable = _expandable
                 base:updateDraw()
                 return node
             end,
@@ -287,4 +287,4 @@ return function(name, basalt)
 
     object.__index = object
     return setmetatable(object, base)
-end
+end