Change "always on" behaviour to simulate always having viewers rather than forcibly keeping inputs active

lib/dtsc.cpp

@@ -1683,13 +1683,13 @@ namespace DTSC{
       trackLock.open(pageName, O_CREAT | O_RDWR, ACCESSPERMS, 1);
       if (!trackLock){
         FAIL_MSG("Could not open semaphore to add track!");
-        return -1;
+        return INVALID_TRACK_ID;
       }
       trackLock.wait();
       if (stream.isExit()){
         trackLock.post();
         FAIL_MSG("Not adding track: stream is shutting down");
-        return -1;
+        return INVALID_TRACK_ID;
       }
     }
 

lib/sdp.cpp

@@ -511,6 +511,11 @@ namespace SDP{
         nope = true;
         tid = myMeta->addTrack();
 
+        if (tid == INVALID_TRACK_ID){
+          WARN_MSG("Could not add new track, skipping");
+          continue;
+        }
+
         // Strip m=
         std::stringstream words(to.substr(2));
         std::string item;