Check if menu item is null before adding assistant new badge

It crashes because there's no assistant in AOSP Contacts.

Bug: 32915307

Test: manual - verified that there's no crash in opening AOSP Contacts
               and that the new badge works well on GoogleContacts.

Change-Id: I3cc14da0c9e50fe0b2f4840645ded8c2563fbc65
diff --git a/src/com/android/contacts/ContactsDrawerActivity.java b/src/com/android/contacts/ContactsDrawerActivity.java
index e348a20..79d0fe2 100644
--- a/src/com/android/contacts/ContactsDrawerActivity.java
+++ b/src/com/android/contacts/ContactsDrawerActivity.java
@@ -265,8 +265,12 @@
         if (mNavigationView == null) {
             return;
         }
-        final LinearLayout newBadgeFrame = (LinearLayout) MenuItemCompat.getActionView(
-                mNavigationView.getMenu().findItem(R.id.nav_assistant));
+        final MenuItem assistantMenu = mNavigationView.getMenu().findItem(R.id.nav_assistant);
+        if (assistantMenu == null) {
+            return;
+        }
+        final LinearLayout newBadgeFrame =
+                (LinearLayout) MenuItemCompat.getActionView(assistantMenu);
         final boolean showWelcomeBadge = !SharedPreferenceUtil.isWelcomeCardDismissed(this);
         if (showWelcomeBadge && newBadgeFrame.getChildCount() == 0) {
             if (mAssistantNewBadge == null) {