Fix a longstanding Server Crash cause

Fixes: CLagCompensationManager::StartLagCompensation with NULL CUserCmd!!!

addons/sourcemod/gamedata/l4d2_null_cusercmd_fix.txt

@@ -0,0 +1,41 @@
+"Games"
+{
+	"left4dead2"
+	{
+		"MemPatches"
+		{
+			"CLagCompensationManager::StartLagCompensation"
+			{
+				"signature"	"CLagCompensationManager::StartLagCompensation"
+
+				// if (!cmd) jump to the return branch.
+
+				"linux"
+				{
+					"offset"	"6CEh"
+					"verify"	"\xC7"
+					"patch"		"\xE9\x32\xFC\xFF\xFF\x90\x90"
+				}
+
+				"windows"
+				{
+					"offset"	"477h"
+					"verify"	"\x68"
+					"patch"		"\xE9\x96\x02\x00\x00"
+				}
+			}
+		}
+
+		"Signatures"
+		{
+			"CLagCompensationManager::StartLagCompensation"
+			{
+				"library"	"server"
+				"linux"		"@_ZN23CLagCompensationManager20StartLagCompensationEP11CBasePlayer19LagCompensationTypeRK6VectorRK6QAnglef"
+				"windows"	"\x55\x8B\xEC\x83\xEC\x64\x53\x33\xC0"
+				/* 55 8B EC 83 EC 64 53 33 C0 */
+			}
+		}
+	}
+}
+

addons/sourcemod/scripting/l4d2_null_cusercmd_fix.sp

@@ -0,0 +1,34 @@
+#pragma semicolon 1
+#pragma newdecls required
+
+#define VERSION	"0.2"
+
+#include <sourcemod>
+#include <sourcescramble> // https://github.com/nosoop/SMExt-SourceScramble
+
+public Plugin myinfo =
+{
+	name = "L4D2 Lag Compensation Null CUserCmd fix",
+	author = "fdxx",
+	description = "Prevent crash: CLagCompensationManager::StartLagCompensation with NULL CUserCmd!!!",
+	version = VERSION,
+}
+
+public void OnPluginStart()
+{
+	Init();
+	CreateConVar("l4d2_null_cusercmd_fix_version", VERSION, "Version", FCVAR_NONE | FCVAR_DONTRECORD);
+}
+
+void Init()
+{
+	GameData hGameData = new GameData("l4d2_null_cusercmd_fix");
+	if (hGameData == null)
+		SetFailState("Failed to load \"l4d2_null_cusercmd_fix.txt\" gamedata.");
+
+	MemoryPatch mPatch = MemoryPatch.CreateFromConf(hGameData, "CLagCompensationManager::StartLagCompensation");
+	if (!mPatch.Validate())
+		SetFailState("Verify patch failed.");
+	if (!mPatch.Enable())
+		SetFailState("Enable patch failed.");
+}

cfg/generalfixes.cfg

@@ -63,6 +63,7 @@ sm plugins load fixes/l4d2_sg552_zoom_fix.smx
 sm plugins load fixes/l4d2_changelevel.smx
 sm plugins load fixes/weapon_spawn_duplicate_fix.smx
 sm plugins load fixes/l4d_fix_common_shove.smx
+sm plugins load fixes/l4d2_null_cusercmd_fix.smx
 
 // Anti-Cheat.
 sm plugins load anticheat/l4d2_noghostcheat.smx