Reliability fixes for nickname valid-checks on client and server

Fix 1: Backtick validation gap (client)
Added strchr(szNick, '') != nullptrcheck to the client's CheckNickProvided, matching the server's version in Shared/Utils.cpp. Previously, a nickname containing a backtick passed all client-side checks, was serialized correctly, and then got rejected server-side with INVALID_NICKNAME.

Fix 2: Unchecked ReadString (server)
Added return-value check on BitStream.ReadString(m_strPlayerVersion). If this read fails (corrupted length prefix from a shifted bitstream), it now returns false immediately instead of continung to parse the nickname and subsequent fields from a wrong offset. This prevents garbage data from being interpreted as the nickname and triggering an incorrect INVALID_NICKNAME.

Author: Dutchman101

Client/core/CConnectManager.cpp

@@ -450,6 +450,8 @@ bool CConnectManager::CheckNickProvided(const char* szNick)
         return false;
     if (stricmp(szNick, "server") == 0)
         return false;
+    if (strchr(szNick, '`') != nullptr)
+        return false;
     return true;
 }
 

Server/mods/deathmatch/logic/packets/CPlayerJoinDataPacket.cpp

@@ -21,7 +21,8 @@ bool CPlayerJoinDataPacket::Read(NetBitStreamInterface& BitStream)
     if (!BitStream.Read(m_usBitStreamVersion))
         return false;
 
-    BitStream.ReadString(m_strPlayerVersion);
+    if (!BitStream.ReadString(m_strPlayerVersion))
+        return false;
 
     m_bOptionalUpdateInfoRequired = BitStream.ReadBit();