fix Pending tasks observer when destroying project
fix Pending tasks observer when destroying project

crewmate/crewmate,irfanah/teambox,nfredrik/teambox,ccarruitero/teambox,codeforeurope/samenspel,crewmate/crewmate,nfredrik/teambox,irfanah/teambox,irfanah/teambox,rahouldatta/teambox,rahouldatta/teambox,vveliev/teambox,codeforeurope/samenspel,vveliev/teambox,ccarruitero/teambox,nfredrik/teambox,vveliev/teambox,irfanah/teambox,crewmate/crewmate,teambox/teambox,rahouldatta/teambox,teambox/teambox,nfredrik/teambox,vveliev/teambox,teambox/teambox