Your configuration specifies to merge with the ref '3.5/master' from the remote, but no such ref was fetched.

1ce6dac..a5ab7de  3.4/bfq    -> origin/3.4/bfq
  fa52ab1..f5d387e  3.4/master -> origin/3.4/master
  398cc33..1c3000a  3.4/upstream-updates -> origin/3.4/upstream-updates
  d01630e..6b612f7  3.7/master -> origin/3.7/master
  491e78a..f49f47f  3.7/misc   -> origin/3.7/misc
  5b7be63..356d8c6  3.7/upstream-updates -> origin/3.7/upstream-updates
  636753a..027c1f3  3.8/master -> origin/3.8/master
  b8e524c..cfcf7b5  3.8/misc   -> origin/3.8/misc
  * [neuer Zweig]     3.8/upstream-updates -> origin/3.8/upstream-updates

git pull origin remotebranch

[branch "sparql"]
    merge = refs/heads/sparql
    remote = origin # <-- added

git fetch origin
git merge origin/master

[branch "Bug/some_branch"]
  remote = origin
  merge = refs/heads/Bug/some_branch

[branch "Bug/some_branch"]
  remote = origin
  merge = refs/heads/bug/some_branch

$ git status
On branch blah_gone_now
Your branch is based on 'origin/1234/blah_gone_now', but the upstream is gone.
  (use "git branch --unset-upstream" to fixup)

$ git branch --unset-upstream