Hello. I had won mission against Sorceress in a space. As she took Aava, my game crashed with error window.

model.lua:0: assertion failed!
stack traceback:
[C]: in function 'assert'
model.lua:in function 'all_render_entities'
model.lua: in function 'set_model_dissolve'
model.lua: in function 'call_hook'
timer.lua: in function 'update_timers'
render.lua: in function 'call_hook'
main.lua: in function 'display'
main.lua: in function <main.lua:0>

Error report has been written to:
C:/Users/username/Documents/Ctrl Alt Ninja/Druidstone/shinobi.log

I have to repeat the whole mission. It will probably happen again. Any advice why this happens?