segfault when pressing cursor up/down in debug mutation menu with all mutations filtered out.

[kevingranade]

Probably a uimenu issue rather than anything to do with the mutation debug menu in particular.
Opened the menu, filtered out everything, and pressed up arrow, resulting in an immediate crash.

Program received signal SIGABRT, Aborted.
0xf7727425 in __kernel_vsyscall ()
(gdb) bt
#0 0xf7727425 in __kernel_vsyscall ()
#1 0x42efbb96 in raise () from /lib/libc.so.6
#2 0x42efd3d3 in abort () from /lib/libc.so.6
#3 0x433d1d92 in __gnu_debug::_Error_formatter::_M_error() const () from /lib/libstdc++.so.6
#4 0x080907bc in std::__debug::vector<int, std::allocator >::operator[](this=0xffc7cf80, __n=4294967295) at /usr/include/c++/4.8.2/debug/vector:346
#5 0x082cf9d4 in uimenu::scrollby (this=0xffc7ceb4, scrollby=-1, key=259) at src/ui.cpp:654
#6 0x082cdcc5 in uimenu::inputfilter (this=0xffc7ceb4) at src/ui.cpp:265
#7 0x082cfabe in uimenu::query (this=0xffc7ceb4, loop=true) at src/ui.cpp:680
#8 0x086b9791 in game::wishmutate (this=0xf7467008, p=0xf74b8334) at src/wish.cpp:193
#9 0x085df63c in game::debug (this=0xf7467008) at src/game.cpp:4524
#10 0x085d9cfd in game::handle_action (this=0xf7467008) at src/game.cpp:3670
#11 0x085c91a9 in game::do_turn (this=0xf7467008) at src/game.cpp:1391
#12 0x084b182c in main (argc=0, argv=0xffc7e418) at src/main.cpp:294

(gdb)