Segfault when killing a Pirate in the Caribbean in binary/ternary tilings

[josephcsible]

When killing a Pirate in the Caribbean in binary or ternary tilings, the game will segfault. The problem is here:

hyperrogue/bigstuff.cpp

Line 128 in 8b7e82b

if(eubinary || c->master->alt) return c->master->alt->alt;

eubinary is true, but c->master->alt is null, so dereferencing it with c->master->alt->alt causes the segfault. I'm not sure what it's supposed to do instead, though.