Fix cross-project milestone ref with invalid project
Fix cross-project milestone ref with invalid project

jirutka/gitlabhq,mmkassem/gitlabhq,mr-dxdy/gitlabhq,daiyu/gitlab-zh,SVArago/gitlabhq,shinexiao/gitlabhq,shinexiao/gitlabhq,openwide-java/gitlabhq,axilleas/gitlabhq,jirutka/gitlabhq,stoplightio/gitlabhq,Soullivaneuh/gitlabhq,htve/GitlabForChinese,openwide-java/gitlabhq,t-zuehlsdorff/gitlabhq,daiyu/gitlab-zh,icedwater/gitlabhq,SVArago/gitlabhq,mmkassem/gitlabhq,axilleas/gitlabhq,mr-dxdy/gitlabhq,SVArago/gitlabhq,iiet/iiet-git,LUMC/gitlabhq,htve/GitlabForChinese,htve/GitlabForChinese,mmkassem/gitlabhq,axilleas/gitlabhq,Soullivaneuh/gitlabhq,darkrasid/gitlabhq,allysonbarros/gitlabhq,t-zuehlsdorff/gitlabhq,stoplightio/gitlabhq,darkrasid/gitlabhq,iiet/iiet-git,jirutka/gitlabhq,iiet/iiet-git,icedwater/gitlabhq,allysonbarros/gitlabhq,martijnvermaat/gitlabhq,LUMC/gitlabhq,dplarson/gitlabhq,screenpages/gitlabhq,iiet/iiet-git,screenpages/gitlabhq,martijnvermaat/gitlabhq,martijnvermaat/gitlabhq,dreampet/gitlab,icedwater/gitlabhq,SVArago/gitlabhq,screenpages/gitlabhq,stoplightio/gitlabhq,Soullivaneuh/gitlabhq,mr-dxdy/gitlabhq,openwide-java/gitlabhq,allysonbarros/gitlabhq,darkrasid/gitlabhq,martijnvermaat/gitlabhq,mr-dxdy/gitlabhq,screenpages/gitlabhq,stoplightio/gitlabhq,jirutka/gitlabhq,t-zuehlsdorff/gitlabhq,htve/GitlabForChinese,mmkassem/gitlabhq,Soullivaneuh/gitlabhq,dreampet/gitlab,axilleas/gitlabhq,icedwater/gitlabhq,openwide-java/gitlabhq,dplarson/gitlabhq,dreampet/gitlab,allysonbarros/gitlabhq,dplarson/gitlabhq,dreampet/gitlab,LUMC/gitlabhq,dplarson/gitlabhq,shinexiao/gitlabhq,LUMC/gitlabhq,daiyu/gitlab-zh,t-zuehlsdorff/gitlabhq,shinexiao/gitlabhq,darkrasid/gitlabhq,daiyu/gitlab-zh