Fixed previous commit (one var can be NULL)

Author: MartinPulec

src/video_rxtx/rtp.cpp

@@ -141,7 +141,7 @@ rtp_video_rxtx::rtp_video_rxtx(map<string, param_u> const &params) :
         }
 
         if ((m_network_devices = initialize_network(m_requested_receiver.c_str(), m_recv_port_number, m_send_port_number,
-                                        m_participants, m_ipv6, m_requested_mcast_if.c_str()))
+                                        m_participants, m_ipv6, m_requested_mcast_if))
                         == NULL) {
                 throw string("Unable to open network");
         } else {
@@ -199,7 +199,7 @@ void rtp_video_rxtx::change_tx_port(int tx_port)
         m_send_port_number = tx_port;
         m_network_devices = initialize_network(m_requested_receiver.c_str(), m_recv_port_number,
                         m_send_port_number, m_participants, m_ipv6,
-                        m_requested_mcast_if.c_str());
+                        m_requested_mcast_if);
         if (!m_network_devices) {
                 throw string("Changing RX port failed!\n");
         }

src/video_rxtx/rtp.h

@@ -76,7 +76,7 @@ class rtp_video_rxtx : public video_rxtx {
         int              m_recv_port_number;
         int              m_send_port_number;
         bool             m_ipv6;
-        std::string      m_requested_mcast_if;
+        const char      *m_requested_mcast_if;
         fec             *m_fec_state;
 private:
         void process_message(struct msg_sender *);

src/video_rxtx/ultragrid_rtp.cpp

@@ -181,7 +181,7 @@ void ultragrid_rtp_video_rxtx::receiver_process_messages()
                         m_network_devices = initialize_network(m_requested_receiver.c_str(),
                                         m_recv_port_number,
                                         m_send_port_number, m_participants, m_ipv6,
-                                        m_requested_mcast_if.c_str());
+                                        m_requested_mcast_if);
                         if (!m_network_devices) {
                                 throw runtime_error("Changing RX port failed!");
                         }