Fix potential crash in block search (#3955)
Fix potential crash in block search (#3955)


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