request #6907: Cannot filter by milestone if there is no other tracker field in the filter

Change-Id: I9be714b1f7fddb63d6a7a6f3df24df0357ba7816
Merge commit 'refs/changes/69/2469/2' of http://gerrit.tuleap.net/tuleap into HEAD

* http://gerrit.tuleap.net/tuleap:
  request #6907: Cannot filter by milestone if there is no other tracker field in the filter

Change-Id: I1e3247da41c67fc920b7c3c338d077e7d54e1283
This is Tuleap 7.0.99.32

Change-Id: I63b4daf8bb28dd84f0ca5990b68562c484daf68a