It seems that there is a bug in LoopMover_Refine_Backrub.cc. When I use this mover in my protocol, my programme exit with en error from BackrubMover::add_segment() function (input pose is null). So I read the code and found that the author may forget to set the input pose. I added two line codes after line 135 in LoopMover_Refine_Backrub.cc. Now it works.
line 134: protocols::moves::BackrubMover backrubmover;
line 135: backrubmover.branchopt().read_database();