File libunity-fix-optional-types.patch of Package libunity

--- a/protocol/protocol-icon.vala
+++ b/protocol/protocol-icon.vala
@@ -185,7 +185,7 @@ public class AnnotatedIcon : Object, GLib.Icon
   }
 
   /* Added to GIcon interface in 2.37 */
-  private Variant serialize ()
+  private Variant? serialize ()
   {
     Variant? ret = null;
     return ret;
--- a/src/unity-scope-channel.vala
+++ b/src/unity-scope-channel.vala
@@ -312,7 +312,7 @@ internal class ScopeChannel : Object
           DBusSignalFlags.NONE, this.owner_changed);
     }
 
-    private void owner_changed (DBusConnection con, string sender_name,
+    private void owner_changed (DBusConnection con, string? sender_name,
                                 string obj_path, string ifc_name,
                                 string sig_name, Variant parameters)
     {