Add validity check to SaveStatsPeriodically_Threaded

[CTalvio]

Simply adds an IsValid check into the foreach player loop in SaveStatsPeriodically_Threaded.

In short, this is causing crashes for the same reason as #767, but far more rarely, as this loop only executes every five seconds, and a player must disconnect at the exact same time it runs. Still, I've had it happen.

[19:55:53] [NORTHSTAR] [info] Player player disconnected: "You were disconnected due to being AFK"
[19:55:53] [NORTHSTAR] [info] Player player disconnected: "You were disconnected due to being AFK"
[19:55:53] [NORTHSTAR] [warn] attempted to write pdata of size 0!
[19:55:53] [SCRIPT SV] [info] SCRIPT ERROR: [SERVER] Persistent data not available.
[19:55:53] [SCRIPT SV] [info]  -> player.SetPersistentVar( key, expect float( player.GetPersistentVar( key ) ) + val )
[19:55:53] [SCRIPT SV] [info]
CALLSTACK
*FUNCTION [Stats_SaveAllStats()] mp/_stats.nut line [93]
*FUNCTION [SaveStatsPeriodically_Threaded()] mp/_stats.nut line [1041]

[19:55:53] [SCRIPT SV] [info] LOCALS
[@ITERATOR@] 5
[val] 8.3329941844568e-005
[key] "timeStats.dead"
[player] ENTITY (player player [9] (player "player" at <-4847.97 -975.969 328.046>))
[this] TABLE
[@ITERATOR@] 9
[player] ENTITY (player player [9] (player "player" at <-4847.97 -975.969 328.046>))
[@INDEX@] 8
[this] TABLE

DIAGPRINTS


abnormal program termination

It may be prudent to look into modifying GetPlayerArray rather than adding these fixes... Though for now I've modded these two in on my servers, and it has drastically reduced crashes.

[CTalvio]

@ASpoonPlaysGames

[ASpoonPlaysGames]

Code looks good

[GeckoEidechse]

This really isn't testable other than hosting a server for a prolonged period of time and checking for script errors. This is basically what @CTalvio did so I'm forgoing testing on my end ^^