Fix Crash (#1066)

* fix possible npe

* Update ConversationViewHolder.java

* revert unneded changes

app/src/main/java/com/keylesspalace/tusky/components/conversation/ConversationViewHolder.java

@@ -107,7 +107,9 @@ public class ConversationViewHolder extends StatusBaseViewHolder {
     private void setConversationName(List<ConversationAccountEntity> accounts) {
         Context context = conversationNameTextView.getContext();
         String conversationName;
-        if(accounts.size() == 1) {
+        if(accounts.size() == 0) {
+            conversationName = " ";
+        }else if(accounts.size() == 1) {
             conversationName = context.getString(R.string.conversation_1_recipients, accounts.get(0).getUsername());
         } else if(accounts.size() == 2) {
             conversationName = context.getString(R.string.conversation_2_recipients, accounts.get(0).getUsername(), accounts.get(1).getUsername());