Null-check tooltip view to avoid race condition crash.

I think this happens if you tap the tooltip just as the dialog times out? Can't hurt to check.

Fixes: 191281724
Test: crashes at least as infrequently as before, probably less
Change-Id: I3c83e775a7fd278dc255242518412ba790625fdb

packages/SystemUI/src/com/android/systemui/volume/VolumeDialogImpl.java

@@ -1127,7 +1127,12 @@ public class VolumeDialogImpl implements VolumeDialog,
                     .alpha(0.f)
                     .setStartDelay(0)
                     .setDuration(mDialogHideAnimationDurationMs)
-                    .withEndAction(() -> mODICaptionsTooltipView.setVisibility(INVISIBLE))
+                    .withEndAction(() -> {
+                        // It might have been nulled out by tryToRemoveCaptionsTooltip.
+                        if (mODICaptionsTooltipView != null) {
+                            mODICaptionsTooltipView.setVisibility(INVISIBLE);
+                        }
+                    })
                     .start();
         }
     }