fix crash when interpolation enabled on linux

[briaguya-ai]

i'm not sure exactly what was going on, but we were getting bad pointers in a bunch of sys_matrix functions when transitioning between screens

all of those functions had gInterpolationMatrix passed in when they were called, and that should be set in

Starship/src/sys/sys_main.c

Line 151 in 537b25a

gInterpolationMatrix = &sInterpolationMatrixStack[0];

so my guess is that we were sometimes getting to those functions before it was being set? (on scene transition of some sort?)

i wish i had a better understanding of why we were getting bad pointers, but doing this makes it so we don't get bad pointers and the game doesn't crash (and it's a tiny 1 line fix that seems reasonable so 🤷 i guess?)