// This:
uint old_rate = t->growth_rate;
if (p2 == TOWN_GROW_RATE_NORMAL)
t->growth_rate = GetNormalGrowthRate(t);
else
t->growth_rate = p2 | TOWN_GROW_RATE_CUSTOM;
// Should be:
uint old_rate = t->growth_rate;
if (p2 == TOWN_GROW_RATE_NORMAL) {
t->growth_rate = GetNormalGrowthRate(t);
} else {
t->growth_rate = p2 | TOWN_GROW_RATE_CUSTOM;
}