According the api, it looks like it should not be expecting parameters to be passed by reference.
The error message reads "Warning: Parameter 1 to page_title_user_cancel() expected to be a reference, value given in module_invoke_all()". The function's signature doesn't match the requirement defined by hook_user_cancel().
The error is still in the dev. The patch #1 looks fine. Go commit it.
This is just to confirm that the patch fixes the problem. We're using it in production and no longer see the error.
Patch #1 works for me! No longer do i see the error.
Patch #1 works for me too!
Bug related in my project.https://drupal.org/node/2027615
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