'collapse-thread' and 'collapse-all': no such function in map

[Yubin Ruan]

Hi mutt developers:

I have two mapping in my rc file as follow:

    bind pager,index - collapse-thread
    bind pager,index _ collapse-all

but there are errors poping up when mutt start up (with the "Press any key to
continue stall"...)

    Error in /home/yubin/.muttrc, line 225: collapse-thread: no such function 
in map
    Error in /home/yubin/.muttrc, line 226: collapse-all: no such function in 
map

However, I can use that key mapping (all functionalities work fine).

I am using Mutt-1.9.1. Is there anything I am doing wrong?

        Yubin