Invitations sent to laptops without an Activity installed are not handled very cleanly

[greenfeld]

1. Have laptop A start an activity which is sharable but not installed on laptop B.
2. Send an invitation from the Network or Friends View of laptop A to laptop B to join a shared session lead by laptop A of that activity.

Expected: Some sort of error message in the GUI telling User A and/or B that we cannot join the activity because it is not installed, preferably using the proper user-friendly name for the activity and not its Sugar-internal name. (Telling User A what is or is not installed on a remote system might be a bit of a security risk though.)

Actual: We see an "unknown" (gray circle) icon flash on laptop B asking us to join the activity. If one looks in the frame on laptop B in the list of activities, said icon also appears with the Sugar-internal name (such as org.laptop.HelloWorld) as the activity to potentially join. Attempting to accept the invite and join the activity results in the icon disappearing from the Frame and nothing happening apart from an exception logged to Sugar's shell.log.

Seen in 11.2.0 os15.

[erikos]

The situation in 0.84:

- A invites B to an activity B does not have installed

- on machine B a chat invitation will appear

- when B clicks on the invitation a chat invitation on A will appear

- if A accepts that, they can chat away

So the current behavior where on B we get the grey circle that one can not remove is a bit of a regression.