Adds an idle-state for the safebutton
Adds an idle-state for the safebutton

When there is no model, the safebutton goes back into the idle state

contributes to #128

bq/Ultimaker-Cura,ad1217/Cura,DeskboxBrazil/Cura,bq/Ultimaker-Cura,ynotstartups/Wanhao,Curahelper/Cura,markwal/Cura,fxtentacle/Cura,totalretribution/Cura,hmflash/Cura,senttech/Cura,fieldOfView/Cura,ad1217/Cura,senttech/Cura,totalretribution/Cura,lo0ol/Ultimaker-Cura,lo0ol/Ultimaker-Cura,fieldOfView/Cura,DeskboxBrazil/Cura,ynotstartups/Wanhao,markwal/Cura,fxtentacle/Cura,Curahelper/Cura,hmflash/Cura