[libepc] Add a missing default switch case.

[Murray Cumming <murrayc src gnome org>]

commit f501d766e761d2739feabd68b25b9db64d920f00
Author: Murray Cumming <murrayc murrayc com>
Date:   Wed Oct 28 11:57:49 2015 +0100

    Add a missing default switch case.

 libepc/publisher.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/libepc/publisher.c b/libepc/publisher.c
index 2e5c6c7..37443d6 100644
--- a/libepc/publisher.c
+++ b/libepc/publisher.c
@@ -911,6 +911,10 @@ epc_publisher_get_bookmark_type (EpcPublisher *self)
 
       case EPC_PROTOCOL_UNKNOWN:
         break;
+
+      default:
+        g_warning ("%s: Unexpected protocol.", G_STRFUNC);
+        break;
     }
 
   return NULL;