Turn BinarySocket::Write() into a no-op when called with l == 0

include/sockets.h

@@ -347,7 +347,7 @@ class CoreExport BinarySocket : public virtual Socket
 
 	/** Write data to the socket
 	 * @param buffer The data to write
-	 * @param l The length of the data
+	 * @param l The length of the data; if 0 then this function returns without doing anything
 	 */
 	virtual void Write(const char *buffer, size_t l);
 	void Write(const char *message, ...);

src/socket_transport.cpp

@@ -167,6 +167,8 @@ bool BinarySocket::ProcessWrite()
 
 void BinarySocket::Write(const char *buffer, size_t l)
 {
+	if (l == 0)
+		return;
 	this->write_buffer.push_back(new DataBlock(buffer, l));
 	SocketEngine::Change(this, true, SF_WRITABLE);
 }