Merge "Fix CellLayout cast exception when drag is canceled" into sc-dev am: 76f5572648 am: bf9d632680 am: e77b13ae11

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

Change-Id: Ieb210a4bc49f6770a99fc57f7110b420981d1b85