local_variables/defined?(TOPLEVEL_CONST) in modules

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/v1_1r@159 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 1 insertions, 0 deletions

diff --git a/string.c b/string.c
index 1d3cdadc7c..1b4a984ad3 100644
--- a/string.c
+++ b/string.c
@@ -429,6 +429,7 @@ str_concat(str1, str2)
 #if 0
     str2 = obj_as_string(str2);
 #else
+    if (NIL_P(str2)) return str1;
     Check_Type(str2, T_STRING);
 #endif
     str_cat(str1, RSTRING(str2)->ptr, RSTRING(str2)->len);