how to remove wrong payee from stock purchase transaction

[Jack Ostroff]

While doing some other file cleanup, I discovered a pair of stock  
transactions (one buy, one sell) which have a payee specified in the  
split for the stock account.  I have no idea how it got there, but I'd  
like to remove it.  Unfortunately, the investment transaction editor  
does not show the payee field.  Is there any way around this other than  
editing the xml manually?  I'm on a version freshly compiled from git  
master.