Fix possible NPE.

src/org/thoughtcrime/securesms/conversation/ConversationFragment.java

@@ -745,8 +745,10 @@ public class ConversationFragment extends Fragment
   }
 
   public void onSearchQueryUpdated(@Nullable String query) {
+    if (getListAdapter() != null) {
       getListAdapter().onSearchQueryUpdated(query);
     }
+  }
 
   public void jumpToMessage(@NonNull Address author, long timestamp, @Nullable Runnable onMessageNotFound) {
     SimpleTask.run(getLifecycle(), () -> {