Cannot assign a tag when the tag is "dropped"

[Lars]

@PGR

Setting a context to ‘dropped’ is similar to deleting it, except it doesn’t actually remove it, so if you look at any previously completed actions which were associated with that context, you’ll still be able to see that association. You wouldn’t be able to see if it you deleted that context entirely from your system.

In short: Once you dropped it, it doesn’t make sense to add it to still active items.