Fix bug with thrown objects interacting with coins.

Fixes SuperTux#1398.

src/object/rock.cpp

@@ -19,6 +19,8 @@
 #include "audio/sound_manager.hpp"
 #include "object/explosion.hpp"
 #include "object/coin.hpp"
+#include "badguy/badguy.hpp"
+#include "object/player.hpp"
 #include "supertux/sector.hpp"
 #include "supertux/tile.hpp"
 #include "util/reader_mapping.hpp"
@@ -129,9 +131,13 @@ Rock::collision(GameObject& other, const CollisionHit& hit)
     if (hit.bottom && physic.get_velocity_y() > 200) {
       auto moving_object = dynamic_cast<MovingObject*> (&other);
       if (moving_object) {
-        //Getting a rock on the head hurts. A lot.
-        moving_object->collision_tile(Tile::HURTS);
-        physic.set_velocity_y(0);
+        auto badguy = dynamic_cast<BadGuy*> (moving_object);
+        auto player = dynamic_cast<Player*> (moving_object);
+        if (badguy || player) {
+          //Getting a rock on the head hurts. A lot.
+          moving_object->collision_tile(Tile::HURTS);
+          physic.set_velocity_y(0);
+        }
       }
     }
     return FORCE_MOVE;