Disable autocomplete for mentions if no suggestion is found and check nulls...

Disable autocomplete for mentions if no suggestion is found and check nulls before replacing on completion

rocket-chat-android-widgets/src/main/java/chat/rocket/android/widget/message/autocomplete/AutocompleteManager.java

@@ -220,6 +220,9 @@ public class AutocompleteManager {
   }
 
   private void replaceSelected(String autocompleteSuggestion) {
+    if (text == null) {
+      return;
+    }
     final String preText = text.substring(0, fromIndex);
     final String postText = text.substring(toIndex);
 

rocket-chat-android-widgets/src/main/java/chat/rocket/android/widget/message/autocomplete/AutocompleteSource.java

@@ -12,7 +12,7 @@ public abstract class AutocompleteSource<A extends AutocompleteAdapter, I extend
       new AutocompleteViewHolder.OnClickListener<I>() {
         @Override
         public void onClick(I autocompleteItem) {
-          if (autocompleteSelected != null) {
+          if (autocompleteSelected != null && autocompleteItem != null) {
             autocompleteSelected.onSelected(getAutocompleteSuggestion(autocompleteItem));
           }
         }

rocket-chat-android-widgets/src/main/java/chat/rocket/android/widget/message/autocomplete/user/UserSource.java

@@ -99,7 +99,7 @@ public class UserSource extends AutocompleteSource<UserAdapter, UserItem> {
 
   @Override
   protected String getAutocompleteSuggestion(UserItem autocompleteItem) {
-    return getTrigger() + autocompleteItem.getSuggestion();
+    return getTrigger() + (autocompleteItem == null ? "" : autocompleteItem.getSuggestion());
   }
 
   private List<UserItem> toUserItemList(List<SpotlightUser> users) {