Error if Canvas:renderTo does not receive a function;
int l_lovrCanvasRenderTo(lua_State* L) {
Canvas* canvas = luax_checktype(L, 1, Canvas);
+ luaL_checktype(L, 2, LUA_TFUNCTION);
lovrGraphicsPushView();
lovrCanvasBind(canvas);
lua_settop(L, 2);
