Merge pull request #1068 from williamchange/fix-export-on-start

Fix 3d panel export menu briefly visible on start

Author: RodZill4

material_maker/panels/preview_3d/preview_3d.tscn

@@ -311,6 +311,7 @@ step = 0.01
 float_only = true
 
 [node name="ExportMenu" type="Button" parent="MainMenu/HBox"]
+visible = false
 custom_minimum_size = Vector2(40, 25)
 layout_mode = 2
 tooltip_text = "Export"