Fixed crash when trying to jump, when no player is spawned.

src/Game/Systems/SoundSystem.cpp

@@ -69,6 +69,9 @@ bool SoundSystem::OnInputCommand(const Events::InputCommand & e)
 
 void SoundSystem::playerJumps()
 {
+    if (!m_LocalPlayer.Valid()) {
+        return;
+    }
     bool grounded = (bool)m_World->GetComponent(m_LocalPlayer.ID, "Physics")["IsOnGround"];
     if (grounded) {
         Events::PlaySoundOnEntity e;