Fix for: error: 'when' expression must be exhaustive, add necessary 'null' branch or 'else' branch instead

AOSP DeskClock contains multiple warnings that become errors when updating to Kotlin 1.7. One such error is that 'when' expressions must be exhaustive (even if all cases are functionally covered). A simple fix for this is to simply add an empty null branch (i.e. null -> { }) at the end of the when statement.

Bug: 237017037

Test: Ran `adb shell am instrument -w  com.android.deskclock.tests` with
output:
Time: 54.056
OK (68 tests)

Change-Id: Icfbeaf6d380efcc17cc02bc8299c9ba64c202d2e
(cherry picked from commit 2d796a4ee72adf6d2016f7650c50b8eb6ec0c8e7)
Merged-In: Icfbeaf6d380efcc17cc02bc8299c9ba64c202d2e
diff --git a/src/com/android/deskclock/alarms/AlarmActivity.kt b/src/com/android/deskclock/alarms/AlarmActivity.kt
index a4caf1a..8d9535d 100644
--- a/src/com/android/deskclock/alarms/AlarmActivity.kt
+++ b/src/com/android/deskclock/alarms/AlarmActivity.kt
@@ -283,6 +283,7 @@
                     }
                     AlarmVolumeButtonBehavior.NOTHING -> {
                     }
+                    null -> { }
                 }
             }
         }
diff --git a/src/com/android/deskclock/timer/TimerItem.kt b/src/com/android/deskclock/timer/TimerItem.kt
index 9cdcca4..a0573cf 100644
--- a/src/com/android/deskclock/timer/TimerItem.kt
+++ b/src/com/android/deskclock/timer/TimerItem.kt
@@ -138,6 +138,7 @@
                     mTimerText.isActivated = true
                     mTimerText.importantForAccessibility = View.IMPORTANT_FOR_ACCESSIBILITY_NO
                 }
+                null -> { }
             }
         }
     }