Fixes a memory leak and some UI bugs for expandable blocks (#3939)
Fixes a memory leak and some UI bugs for expandable blocks (#3939)


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