Fix paintbooth crashing when toggling search icon twice

Fixes: 160921175
Test: Manually
Change-Id: I06b13f3b92911634ebceea176496ff5853295dfc
diff --git a/car-ui-lib/tests/paintbooth/src/com/android/car/ui/paintbooth/toolbar/ToolbarActivity.java b/car-ui-lib/tests/paintbooth/src/com/android/car/ui/paintbooth/toolbar/ToolbarActivity.java
index 938f448..f32818a 100644
--- a/car-ui-lib/tests/paintbooth/src/com/android/car/ui/paintbooth/toolbar/ToolbarActivity.java
+++ b/car-ui-lib/tests/paintbooth/src/com/android/car/ui/paintbooth/toolbar/ToolbarActivity.java
@@ -320,7 +320,7 @@
         Mutable<Boolean> showingLauncherIcon = new Mutable<>(false);
         mButtons.add(Pair.create(getString(R.string.toolbar_toggle_search_icon), v -> {
             if (showingLauncherIcon.value) {
-                toolbar.setSearchIcon(0);
+                toolbar.setSearchIcon(null);
             } else {
                 toolbar.setSearchIcon(R.drawable.ic_launcher);
             }