1.0.5dev: Correct `MilestoneOperation` workflow hint when milestone doesn't exist. Refs #11962.
1.0.5dev: Correct `MilestoneOperation` workflow hint when milestone doesn't exist. Refs #11962.

Also, avoid traceback when `set_milestone` workflow attribute is missing.


git-svn-id: 3bd1c7f5b9365705bff4dd56977498491f5ac132@13777 af82e41b-90c4-0310-8c96-b1721e28e2e2

exocad/exotrac,exocad/exotrac,exocad/exotrac,exocad/exotrac