[glibmm] Tests: Initialize a member variable.

[Murray Cumming <murrayc src gnome org>]

commit 7c7becf4509a31b434ae55952140c8eacf0a0fe2
Author: Murray Cumming <murrayc murrayc com>
Date:   Mon Dec 12 10:55:20 2016 +0100

    Tests: Initialize a member variable.
    
    Noticed by cppcheck.

 tests/glibmm_interface_move/main.cc |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/tests/glibmm_interface_move/main.cc b/tests/glibmm_interface_move/main.cc
index 1685b33..16fa72a 100644
--- a/tests/glibmm_interface_move/main.cc
+++ b/tests/glibmm_interface_move/main.cc
@@ -109,7 +109,7 @@ class TestInterface : public Glib::Interface
 protected:
   using CppClassType = TestInterface_Class;
 
-  TestInterface() : Glib::Interface(derived_interface_class_.init()) {}
+  TestInterface() : Glib::Interface(derived_interface_class_.init()), i_(0) {}
 
 public:
   // A real application would never make the constructor public.