[folks] Add a default implementation of TrfPersona.calendar_event_id

[Philip Withnall <pwithnall src gnome org>]

commit 0aec7fb049e7490a279f6c4ff22c9d0ed0673cf3
Author: Philip Withnall <philip tecnocode co uk>
Date:   Sun Jul 10 19:42:25 2011 +0100

    Add a default implementation of TrfPersona.calendar_event_id
    
    It was missing; it might as well return a sensible default value and not
    allow setting of the value rather than doing nothing.

 backends/tracker/lib/trf-persona.vala |   10 +++++++++-
 1 files changed, 9 insertions(+), 1 deletions(-)
---
diff --git a/backends/tracker/lib/trf-persona.vala b/backends/tracker/lib/trf-persona.vala
index 1fd58a4..7270bd5 100644
--- a/backends/tracker/lib/trf-persona.vala
+++ b/backends/tracker/lib/trf-persona.vala
@@ -202,7 +202,15 @@ public class Trf.Persona : Folks.Persona,
         }
     }
 
-  public string calendar_event_id { get; set; }
+  /**
+   * { inheritDoc}
+   */
+  public string calendar_event_id
+    {
+      /* Unsupported */
+      get { return null; }
+      private set {}
+    }
 
   private HashSet<Role> _roles;
   private Set<Role> _roles_ro;