Fixing startup issue

Per @954

rootfs/webapp/acarshub.py

@@ -447,7 +447,8 @@ def init_listeners(special_message=""):
         )
         thread_scheduler = Thread(target=scheduled_tasks)
         thread_scheduler.start()
-    if not thread_html_generator.is_alive():
+    # check if 'g' is not in thread_html_generator
+    if not hasattr(thread_html_generator, "g"):
         acarshub_logging.log(
             f"{special_message}Starting htmlListener",
             "init",
@@ -736,7 +737,7 @@ def main_connect():
         acarshub_logging.acars_traceback(e, "webapp")
 
     # Start the htmlGenerator thread only if the thread has not been started before.
-    if not thread_html_generator.is_alive():
+    if not hasattr(thread_html_generator, "g"):
         sys.stdout.flush()
         thread_html_generator_event.clear()
         thread_html_generator = socketio.start_background_task(htmlListener)

rootfs/webapp/requirements.txt

@@ -1,8 +1,7 @@
 eventlet==0.33.3
 Flask==2.3.3
 Flask-SocketIO==5.3.6
-gunicorn[eventlet] @ git+https://github.com/benoitc/gunicorn.git@48eda22a4b3399b0a65677619b4938503cc207cb
-pyrtlsdr==0.3.0
+gunicorn[eventlet]==21.2.0
 requests==2.31.0
 rrdtool==0.1.16
 schedule==1.2.0