Flowers and mushrooms cannot exist if there is nothing below them

src/main.cpp

@@ -773,6 +773,15 @@ int main(int argc, char** argv)
 							the_accessor->set_id_safe(px, py, pz, id_water);
 						}
 
+						// Flowers and mushrooms cannot exist if there is 
+						// nothing below them.
+
+						block_id plant_above = the_world->get_id_safe(px, py - 1, pz);
+
+						if (plant_above == id_dandelion || plant_above == id_rose || plant_above == id_red_mushroom || plant_above == id_brown_mushroom)
+						{
+							the_world->set_id_safe(px, py - 1, pz, id_air);
+						}
 						block_timer = 10;
 
 						break;