Fix 50e08f333a: Creating a cargo subsidy with town as source did not consider min population. (#7493)

src/subsidy.cpp

@@ -333,6 +333,7 @@ bool FindSubsidyTownCargoRoute()
 
 	/* Select a random town. */
 	const Town *src_town = Town::GetRandom();
+	if (src_town->cache.population < SUBSIDY_CARGO_MIN_POPULATION) return false;
 
 	CargoTypes town_cargo_produced = src_town->cargo_produced;