Fixed failed assertion when non-damageable objects get fall damage (closes #764)

src/physics/physics.cpp

@@ -1576,12 +1576,15 @@ bool CPhysics::EventFrame(const Event &event)
     SoundMotor(event.rTime);
 
     if ( m_bLand && m_fallingHeight != 0.0f ) // if fell
+    {
+        if (m_object->Implements(ObjectInterfaceType::Damageable))
         {
             float force = (m_fallingHeight - m_object->GetPosition().y) * m_fallDamageFraction;
             if (m_object->DamageObject(DamageType::Fall, force))
             {
                 return false; // ugly hack, but works for 0.1.6 release :/
             }
+        }
         m_fallingHeight = 0.0f;
     }