BACKPORT: groupby.apply incorrectly dropping nan #43236#43426

jreback merged 2 commits intopandas-dev:1.3.xpandas-dev/pandas:1.3.xfrom

debnathshoham:auto-backport-of-pr-43236-on-1.3.xdebnathshoham/pandas:auto-backport-of-pr-43236-on-1.3.xCopy head branch name to clipboard