Network: Fix serialization version checks (#15477)

This fixes some incorrect assumptions that the read and write version ranges are identical - whereas they're in fact not.

src/server/clientiface.cpp

@@ -8,6 +8,7 @@
 #include "network/connection.h"
 #include "network/serveropcodes.h"
 #include "remoteplayer.h"
+#include "serialization.h" // SER_FMT_VER_INVALID
 #include "settings.h"
 #include "mapblock.h"
 #include "serverenvironment.h"
@@ -51,6 +52,8 @@ std::string ClientInterface::state2Name(ClientState state)
 }
 
 RemoteClient::RemoteClient() :
+	serialization_version(SER_FMT_VER_INVALID),
+	m_pending_serialization_version(SER_FMT_VER_INVALID),
 	m_max_simul_sends(g_settings->getU16("max_simultaneous_block_sends_per_client")),
 	m_min_time_from_building(
 		g_settings->getFloat("full_block_send_enable_min_time_from_building")),

src/server/clientiface.h

@@ -7,7 +7,6 @@
 #include "irr_v3d.h"                   // for irrlicht datatypes
 
 #include "constants.h"
-#include "serialization.h"             // for SER_FMT_VER_INVALID
 #include "network/networkpacket.h"
 #include "network/networkprotocol.h"
 #include "network/address.h"
@@ -219,7 +218,7 @@ public:
 	//       Also, the client must be moved to some other container.
 	session_t peer_id = PEER_ID_INEXISTENT;
 	// The serialization version to use with the client
-	u8 serialization_version = SER_FMT_VER_INVALID;
+	u8 serialization_version;
 	//
 	u16 net_proto_version = 0;
 
@@ -333,7 +332,7 @@ public:
 
 private:
 	// Version is stored in here after INIT before INIT2
-	u8 m_pending_serialization_version = SER_FMT_VER_INVALID;
+	u8 m_pending_serialization_version;
 
 	/* current state of client */
 	ClientState m_state = CS_Created;