BTS: Merging bugs not working because of "forwarded" to upstream bug

[c.buhtz@posteo.jp]

Hello,

I try to understand a problem with the Bug Tracking System. I tried to 
merge two bugs because one is a duplicate. I send to control@

    merge 985631 985256

I also tried the other way around switching the numbers.

But I got back that message that I don't understand. The link to the 
upstream bug might be a problem but I don't understand why.

Bug #985631 [backintime-qt] backintime-qt: for volumes mounted on 
demand, exiting backupintime-qt during the backup fails
Unable to merge bugs because:
forwarded of #985256 is '' not 
'https://github.com/bit-team/backintime/issues/724'
Failed to merge 985631: Did not alter merged bugs.

Kind
Christian