odd display of waiting for when guest

[burnettk]

set up a process model with public/guest tasks. when a human task is waiting on the guest user, view the process instance as another user. it displays: "This next task is assigned to user(s): , . There is no action for you to take at this time."

it's probably better to show something like this other message that is sometimes used:

"This next task is assigned to a different person or team. There is no action for you to take at this time."

originally discovered in the context of #979 (the 11th documented issue on there).