fix loading of last opened file in editor
fix loading of last opened file in editor

Microsoft/pxt,playi/pxt,Microsoft/pxt,switch-education/pxt,Microsoft/pxt,playi/pxt,playi/pxt,Microsoft/pxt,switch-education/pxt,switch-education/pxt,switchinnovations/pxt,switchinnovations/pxt,switchinnovations/pxt,playi/pxt,switch-education/pxt,switch-education/pxt,switchinnovations/pxt,Microsoft/pxt