[glom/gtkmm4v4] Avoid use of uninitialized variable.

[Murray Cumming <murrayc src gnome org>]

commit 7265bc86ddc7c3cb49f1065c1467810ea8d9b0c2
Author: Murray Cumming <murrayc murrayc com>
Date:   Mon May 29 17:02:02 2017 +0200

    Avoid use of uninitialized variable.
    
    Found by clang++.

 glom/utils_ui.cc |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/glom/utils_ui.cc b/glom/utils_ui.cc
index ba28bdf..e6b3f40 100644
--- a/glom/utils_ui.cc
+++ b/glom/utils_ui.cc
@@ -226,8 +226,8 @@ Glib::RefPtr<Gdk::Pixbuf> UiUtils::get_pixbuf_for_gda_value(const Gnome::Gda::Va
 
   if(value.get_value_type() == GDA_TYPE_BINARY || value.get_value_type() == GDA_TYPE_BLOB)
   {
-    glong buffer_binary_length;
-    gconstpointer buffer_binary;
+    glong buffer_binary_length = 0;
+    gconstpointer buffer_binary = nullptr;
     if(value.get_value_type() == GDA_TYPE_BLOB)
     {
       const auto blob = value.get_blob();