adapt code to LRC API change

LRC API (Singleton's implementation) has changed.
This patch adapats the code to these changes.
Moslty changes deferencement '->' for direct access '.'

Tuleap: #44
Change-Id: Ic87b1306a1239fdb8a6af0affe1ecbc1d16f609c
diff --git a/src/native/dbuserrorhandler.cpp b/src/native/dbuserrorhandler.cpp
index e98afa0..ee1be0f 100644
--- a/src/native/dbuserrorhandler.cpp
+++ b/src/native/dbuserrorhandler.cpp
@@ -107,7 +107,7 @@
 
     gtk_widget_destroy(warning_dialog);
 
-    if ((!CallModel::instance()->isConnected()) || (!CallModel::instance()->isValid())) {
+    if ((!CallModel::instance().isConnected()) || (!CallModel::instance().isValid())) {
         g_warning("could not reconnect to the daemon");
 
         auto quit_dialog = ring_quitting_dialog();