fix  https://github.com/sagemathinc/smc/issues/1707 -- "exception in course/main: handle_projects_store_update"
fix  https://github.com/sagemathinc/smc/issues/1707 -- "exception in course/main: handle_projects_store_update"

sagemathinc/smc,tscholl2/smc,tscholl2/smc,tscholl2/smc,DrXyzzy/smc,tscholl2/smc,tscholl2/smc,sagemathinc/smc,sagemathinc/smc,DrXyzzy/smc,DrXyzzy/smc,DrXyzzy/smc,sagemathinc/smc