[#2850] Fix duplicate ui log entries

deluge/log.py

@@ -151,6 +151,13 @@ def setup_logger(level="error", filename=None, filemode="w", logrotate=None, twi
     )
 
     handler.setFormatter(formatter)
+
+    # Check for existing handler to prevent duplicate logging.
+    if root_logger.handlers:
+        for handle in root_logger.handlers:
+            if not isinstance(handle, type(handler)):
+                root_logger.addHandler(handler)
+    else:
         root_logger.addHandler(handler)
     root_logger.setLevel(level)