WebGL UNET Mozilla FireFox issue

Hi! Maybe someone can help me.
My projects works nicely when I LAN Host from editor + connect from WebGl from Google Chrome.
But I have an error when try do it in Mozilla FireFox(simplest projects works in Mozilla normaly)

Warning message on Host when I trying connect:
"Empty player list given to NetworkServer.Destroy(), nothing to do.
UnityEngine.Networking.NetworkIdentity:UNetStaticUpdate()"

Does anybody know what's the problem?