fix : disallow multiple contacts with same ring id

Change-Id: I9d38babdef507d4e4619ab007442e1517d3711d1
Tuleap: #790
diff --git a/MainPage.xaml.cpp b/MainPage.xaml.cpp
index 140a76b..ae7bda2 100644
--- a/MainPage.xaml.cpp
+++ b/MainPage.xaml.cpp
@@ -343,8 +343,8 @@
 

 void RingClientUWP::MainPage::OncloseMessageTextPage()

 {

-    auto smartPanel = dynamic_cast<SmartPanel^>(_smartPanel_->Content);

-    smartPanel->unselectContact();

+    SmartPanelItemsViewModel::instance->_selectedItem = nullptr;

+    showFrame(_welcomeFrame_);

 }