Revert "SystemUI: prevent NPE on clear recents double press"

This reverts commit 11dd4ce8d0d3a217e05ff83d7ebad73fc190fbcd.
Revert "Recents: ClearAll: Fix glitch on quick double tap"

This reverts commit a4415e76b70e7da09a26bccf66bdf74999c43953.
Revert "Recents: Clear all button for recent apps."

This reverts commit 658fef883595c0a06ed9ee35e28c168ea1a968f2.