Introduction accept/decline buttons don't work for second attempt

Steps to reproduce:

• Add devices A and B as contacts
• Add devices B and C as contacts
• B offers to introduce A to C
• A accepts
• C declines
• B offers to introduce A to C again (A and C must receive the new offers before their screens turn off)
• Expected: A and C can use the accept and decline buttons
• Actual: The accept and decline buttons are unresponsive until the screen has been turned off and on (sometimes it's necessary to leave and re-enter the conversation)

I suspect this is a view recycling issue - IIRC we disable the buttons after they've been pressed once, to avoid issues with multiple taps. If the view gets recycled, I guess the buttons are still disabled.

I saw this while testing !1067 (merged), but I don't think it was introduced by that branch - I've seen it before but never came up with steps to reproduce it. It might also happen for forum/blog/group invitations.