My patch also removes checking of ddeexec presence, so C::B will not complain on start.
Sorry, I didn't see this thread in advance so I answered to the ticket. I'll add my answer here, too for the record:
One note: From what I see this removes the DDE feature completely. DDE could also used on Windows to automate build processes, if properly used. So while this patch indeed fixes the bug mentioned but also removes the ability to script-control C::B from outside in case you really use just one instance (which is an option).
So this solution is not perfect... just my 2 cents here.
A better solution is to check if you are in single instance mode and then allow DDE commands. Additionally besides opening a file we could literally add any operation via DDE to kind of "remote-control" C::B. I do so for other applications at my work, also using the wx-DDE mechanisms with nice benefits.