Do not call refresh_from_data if there is no data
Do not call refresh_from_data if there is no data

Fixes https://github.com/kivy-garden/garden.recycleview/issues/1.
janssen/kivy,rafalo1333/kivy,aron-bordin/kivy,matham/kivy,inclement/kivy,LogicalDash/kivy,rnixx/kivy,jkankiewicz/kivy,rafalo1333/kivy,el-ethan/kivy,andnovar/kivy,darkopevec/kivy,jegger/kivy,andnovar/kivy,aron-bordin/kivy,rnixx/kivy,akshayaurora/kivy,el-ethan/kivy,manthansharma/kivy,autosportlabs/kivy,jegger/kivy,Cheaterman/kivy,aron-bordin/kivy,darkopevec/kivy,kived/kivy,Cheaterman/kivy,inclement/kivy,autosportlabs/kivy,bionoid/kivy,matham/kivy,el-ethan/kivy,kivy/kivy,kivy/kivy,LogicalDash/kivy,darkopevec/kivy,akshayaurora/kivy,jkankiewicz/kivy,jkankiewicz/kivy,jegger/kivy,manthansharma/kivy,janssen/kivy,LogicalDash/kivy,janssen/kivy,andnovar/kivy,manthansharma/kivy,jkankiewicz/kivy,aron-bordin/kivy,rafalo1333/kivy,KeyWeeUsr/kivy,kived/kivy,bionoid/kivy,bionoid/kivy,matham/kivy,KeyWeeUsr/kivy,darkopevec/kivy,KeyWeeUsr/kivy,tony/kivy,janssen/kivy,manthansharma/kivy,LogicalDash/kivy,autosportlabs/kivy,matham/kivy,tony/kivy,tony/kivy,kived/kivy,bionoid/kivy,Cheaterman/kivy,jegger/kivy,rnixx/kivy,akshayaurora/kivy,kivy/kivy,inclement/kivy,KeyWeeUsr/kivy,Cheaterman/kivy