[fix] do not reload engines twice if started with debug mode

searx/webapp.py

 
 
 def run():
-    initialize_engines(settings['engines'])
+    if not searx_debug or os.environ.get("WERKZEUG_RUN_MAIN") == "true":
+        initialize_engines(settings['engines'])
+
     app.run(
         debug=searx_debug,
         use_debugger=searx_debug,