Chat: Fix possible nullptr access (#1238)

Fixes a possible nullptr access.  This is the only call to GetPlayerData where we do not check the result for some reason, so this PR adds in the check and a resulting log line.

Code compiles, unsure how to reproduce the issue, however here is the crash dump I used to deduce this being the possible issue

```

Error: signal 11:
[00] CatchUnhandled(int)(+0x316) [0x561469100336]
[01] /lib/x86_64-linux-gnu/libc.so.6(+0x42520) [0x7f65e8e45520]
[02] /DarkflameServer/build/ChatServer(+0x32719) [0x5614690fa719]
[03] HandlePacket(Packet*)(+0x2a0) [0x5614690fcfb0]
[04] /DarkflameServer/build/ChatServer(main+0x92e) [0x5614690fb75e]
[05] /lib/x86_64-linux-gnu/libc.so.6(+0x29d90) [0x7f65e8e2cd90]
[06] /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0x80) [0x7f65e8e2ce40]
[07] /DarkflameServer/build/ChatServer(_start+0x25) [0x5614690fc375]
```

dChatServer/ChatPacketHandler.cpp

@@ -118,6 +118,11 @@ void ChatPacketHandler::HandleFriendRequest(Packet* packet) {
 	inStream.Read(isBestFriendRequest);
 
 	auto requestor = playerContainer.GetPlayerData(requestorPlayerID);
+	if (!requestor) {
+		LOG("No requestor player %llu sent to %s found.", requestorPlayerID, playerName.c_str());
+		return;
+	}
+
 	if (requestor->playerName == playerName) {
 		SendFriendResponse(requestor, requestor, eAddFriendResponseType::MYTHRAN);
 		return;