I tried to salvage 'flexible linen pants' and the game crashed.

You're on the most recent version of the game 0.2.4.1? There were issues in previous versions with items under certain conditions causing crashes but I haven't encountered them again since. Did another copy of linen pants happen to disappear when you salvaged? Was your inventory full? If it's possible more details are helpful :) but I know it can be difficult when you aren't expecting something to go wrong

If you sent crash report then you're probably on v0.2.3, all reports related to inventory are from that version. As Rebelbeta mentioned the issue is resolved in v0.2.4.1, if you update, the duplicated pants should be removed from your inventory.