[libgxps] Fix useless warnings

[Ignacio Casal Quinteiro <icq src gnome org>]

commit fa58bd6a953011b72153a37e2cd470af5375f995
Author: Ignacio Casal Quinteiro <ignacio casal nice-software com>
Date:   Fri Sep 9 15:48:42 2016 +0200

    Fix useless warnings
    
    https://bugzilla.gnome.org/show_bug.cgi?id=771057

 libgxps/gxps-glyphs.c |    2 ++
 libgxps/gxps-path.c   |    4 ++++
 2 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/libgxps/gxps-glyphs.c b/libgxps/gxps-glyphs.c
index ed52898..ac7bd4b 100644
--- a/libgxps/gxps-glyphs.c
+++ b/libgxps/gxps-glyphs.c
@@ -106,6 +106,8 @@ glyphs_indices_token_type_to_string (GlyphsIndicesTokenType type)
         default:
                 g_assert_not_reached ();
         }
+
+        return NULL;
 }
 
 static gboolean
diff --git a/libgxps/gxps-path.c b/libgxps/gxps-path.c
index 4f5c2f6..b14001d 100644
--- a/libgxps/gxps-path.c
+++ b/libgxps/gxps-path.c
@@ -97,6 +97,8 @@ path_data_token_type_to_string (PathDataTokenType type)
         default:
                 g_assert_not_reached ();
         }
+
+        return NULL;
 }
 
 #ifdef GXPS_ENABLE_DEBUG
@@ -122,6 +124,8 @@ print_token (PathDataToken *token)
         default:
                 g_assert_not_reached ();
         }
+
+        return NULL;
 }
 #endif /* GXPS_ENABLE_DEBUG */