I recently fixed an identical separation on my Jack Casady bass. I used standard super glue injected via a very small syringe, but I did get some smear on the neck. I got it off with acetone, which fortunately didn't affect the finish on the Casady.
I liked the suggestion I got (post facto) of thinning some Titebond with water so it would flow through the syringe, and injecting it. Clamp and set time would be much longer, but it would have cleaned up more easily.
When I held the body and twisted the neck at the headstock the cracks would open slightly, so that helped me get the glue in the right place. My wife helped by doing the twisting while I injected the glue.
