added test for data uri without mime type

test/io_adapters/data_uri_adapter_test.rb

@@ -8,6 +8,11 @@ class DataUriAdapterTest < Test::Unit::TestCase
     end
   end
 
+  should 'allow a missing mime-type' do
+    adapter = Paperclip.io_adapters.for("data:;base64,#{original_base64_content}")
+    assert_equal Paperclip::DataUriAdapter, adapter.class
+  end
+
   context "a new instance" do
     setup do
       @contents = "data:image/png;base64,#{original_base64_content}"