test_sdbm.rb: only if SDBM

* test/sdbm/test_sdbm.rb (TestSDBM): test only if SDBM is loadable.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41489 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/sdbm/test_sdbm.rb

@@ -538,5 +538,5 @@ class TestSDBM < Test::Unit::TestCase
     end
     assert_raise(ArgumentError) { @sdbm.update(obj) }
   end
-end
+end if defined? SDBM