Fix NPE: hasFullScreenIntent

Clear headsUpEntryShowing on shade open so that we don't try to
update a null mEntry of the previously showing hun when shade closes

Fixes: 355355815
Test: treehugger
Flag: com.android.systemui.notification_avalanche_throttle_hun
Change-Id: I2ef7f6dfee6689c5deef6af1d4d1caa59b0efe48
2 files changed