Material Stool Error!

This seems to only happen on Stranded servers…
Warning: vgui.Create failed to create the VGUI component (MatSelect)
sandbox\gamemode\spawnmenu\controlpanel.lua:99: ControlPanelBuildFunction Error:
sandbox\gamemode\spawnmenu\controlpanel.lua:63: attempt to index local ‘MatSelect’ (a nil value)
Any suggestions on how to fix this?