set zm_terminate instead of exit() so that all the cleanup code happens

src/zm_eventstream.cpp

@@ -842,7 +842,8 @@ void EventStream::runStream() {
 
   if (!event_data) {
     sendTextFrame("No event data found");
-    exit(0);
+    zm_terminate = true;
+    return;
   }
 
   double fps = 1.0;