[glibmm] VariantDict::lookup_value(): Return soon enough on failure.

[Murray Cumming <murrayc src gnome org>]

commit b30fd8424fe409132098ce60971e44738a027c2c
Author: Murray Cumming <murrayc murrayc com>
Date:   Fri Apr 4 12:17:13 2014 +0200

    VariantDict::lookup_value(): Return soon enough on failure.

 glib/src/variantdict.hg |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/glib/src/variantdict.hg b/glib/src/variantdict.hg
index 47ed5f6..876591f 100644
--- a/glib/src/variantdict.hg
+++ b/glib/src/variantdict.hg
@@ -123,6 +123,8 @@ bool VariantDict::lookup_value(const Glib::ustring& key, T_Value& value) const
 
   Glib::VariantBase variantBase;
   const bool result = lookup_value_variant(key, type_glib_variant::variant_type(), variantBase);
+  if(!result)
+    return result;
 
   try
   {