[PATCH] Rails 3 prototype_helper causes exception when content_tags are nested within blocks

Note: This is in Rails 3
The prototype_helper initializes a JavaScriptGenerator and passes in an empty array to with_output_buffer.
If a content_tag is passed into another content tag via a block, the output_buffer is set to an empty array, which then tries to call 'encoding' on it and fails.

I've attached a failing test, and a patch to make the test pass.