At your stage in the quest line you must complete The Jagged Crown before Season Unending. This was intentionally implemented by the developers to prevent this quest conflicting with the civil war quest line. It sounds like "Talk to Galmar" is your current objective for that quest, but he only speaks of the treaty?
Firstly, keep pestering Galmar. Talk to him over and over, interrupt him if you have to. This may get him to speak the dialog you're looking for.
If that doesn't work, reload the last save (most likely after just entering High Hrothgar) and speak to Galmar before anyone else, this may prevent Season Unending progressing too far and changing his dialog.
As a last resort, if you can return to a save prior to starting Season Unending that will allow you to complete The Jagged Crown. Then you should be able to do Season Unending without issue (not this issue anyway!).
Also, make sure the game is updated to the latest version.
Most Many bugs will be quelled by official updates.