[libchamplainmm] MapSourceDesc: remove compiler warning

[Juan R. Garcia Blanco <juanrgar src gnome org>]

commit 425fe65e61cde94d0cf13efad5e21da2c685d784
Author: Juan R. García Blanco <juanrgar gmail com>
Date:   Fri Aug 1 22:57:22 2014 +0200

    MapSourceDesc: remove compiler warning

 champlain/src/map-source-desc.ccg |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/champlain/src/map-source-desc.ccg b/champlain/src/map-source-desc.ccg
index 268af16..b0b1517 100644
--- a/champlain/src/map-source-desc.ccg
+++ b/champlain/src/map-source-desc.ccg
@@ -22,6 +22,7 @@ namespace Champlain
 static ChamplainMapSource* MapSource_constructor_callback(ChamplainMapSourceDesc* desc)
 {
   // TODO
+  return NULL;
 }
 
 } // namespace Champlain