Merge "Fix CellLayout cast exception when drag is canceled" into sc-dev am: 76f5572648 am: c13b47f7bf

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/14948453

Change-Id: I77835904fcbef8110d6880566a785999c8d98f79