Fixing bug #6244. Unable to remove contributor semantic

Change-Id: I44c479aae8e020ffae9572694e2c21a41e323a0e
Merge commit 'refs/changes/24/1924/2' of ssh://gerrit.tuleap.net:29418/tuleap into stable

* ssh://gerrit.tuleap.net:29418/tuleap:
  Fixing bug #6244. Unable to remove contributor semantic

Change-Id: I682a8aa084bec939598880230d9655f60707c42f
This is Tuleap 6.10.99.24

Change-Id: I49b2c5b7404488cfc8f94ae7a7b0733b91f574e7