Possible null ref in SteamNetworkingSocketsTransport.CloseP2PSessions().

[TheJohnGamble]

NetworkManager.Singleton is not guaranteed to exist when calling CloseP2PSessions, such as in the case of exiting play mode while hosting a server. NetworkManager can set its Singleton to null before it is destroyed, which caused a null ref here.

Suggested fix:

Change the line:

if (NetworkManager.Singleton.LogLevel <= LogLevel.Developer)

to

if (NetworkManager.Singleton && NetworkManager.Singleton.LogLevel <= LogLevel.Developer)