skypopen: fixing bug from Anton VG, adding some guards against NULL sessions and channels

src/mod/endpoints/mod_skypopen/mod_skypopen.c

@@ -938,6 +938,8 @@ static switch_status_t channel_read_frame(switch_core_session_t *session, switch
 						char *p = digit_str;
 						switch_channel_t *channel = switch_core_session_get_channel(session);
 
+						if(channel){
+
 							while (p && *p) {
 								switch_dtmf_t dtmf;
 								dtmf.digit = *p;
@@ -948,6 +950,9 @@ static switch_status_t channel_read_frame(switch_core_session_t *session, switch
 							NOTICA("DTMF DETECTED: [%s] new_dtmf_timestamp: %u, delta_t: %u\n", SKYPOPEN_P_LOG, digit_str, (unsigned int) new_dtmf_timestamp,
 									(unsigned int) (new_dtmf_timestamp - tech_pvt->old_dtmf_timestamp));
 							tech_pvt->old_dtmf_timestamp = new_dtmf_timestamp;
+						}else{
+							WARNINGA("NO CHANNEL ?\n", SKYPOPEN_P_LOG);
+						}
 					}
 				}
 			}
@@ -2138,6 +2143,7 @@ int dtmf_received(private_t *tech_pvt, char *value)
 	switch_channel_t *channel = NULL;
 
 	session = switch_core_session_locate(tech_pvt->session_uuid_str);
+	if (session) {
 		channel = switch_core_session_get_channel(session);
 
 		if (channel) {
@@ -2165,6 +2171,9 @@ int dtmf_received(private_t *tech_pvt, char *value)
 			WARNINGA("received %c DTMF, but no channel?\n", SKYPOPEN_P_LOG, value[0]);
 		}
 		switch_core_session_rwunlock(session);
+	}else{
+		WARNINGA("received %c DTMF, but no session?\n", SKYPOPEN_P_LOG, value[0]);
+	}
 
 	return 0;
 }