NetClient FSM error when pausing while others are loading

[elexis]

If a multiplayergame starts, one client having finished the loading screen and pausing while the others are still loading (or synchronizing?), the following error occurs for that loading client and it doesn't show the pause overlay to the client once it's finished:

Net client: Error running FSM update (type=21 state=6)

type 21 is NMT_CLIENT_PAUSED, state 6 is NCS_LOADING (can perhaps occur with NCS_JOIN_SYNCING too)

Error message reported by siole. I could not reproduce this issue locally (since the two instances load simultaenously, and since rejoins seem properly implemented), but it occured in two games for multiple clients (on caledonian meadows, which is a slow loading map). The pause packet was introduced in r18204, #1950.

• NMT means NetMessageType and is defined in NetMessages.h
• NSS means NetServerSessionState and is defined in NetServer.h
• NCS means NetClient state and is defined in NetClient.h

[elexis]

In alpha 22 it's:

ERROR: Net client: Error running FSM update (type=22 state=6)

IIRC there is also the issue with the pausing screen not shown if the game was paused by someone else while in loading screen.

[Imarok]

refs ​https://code.wildfiregames.com/rP18204

[Imarok]

In 19563:

Avoid NetClient FSM error when pausing while loading the game.
Patch by echotangoecho. Closes rP18204. Fixes #4261.

Differential Revision: ​https://code.wildfiregames.com/D472