🐛 fix(base.py): change custom_fields default value from an empty list to a defaultdict to prevent potential errors

The custom_fields attribute in the FrontendNode class now has a default value of defaultdict(list) instead of an empty list. This change ensures that custom_fields is always a defaultdict, which prevents potential errors when accessing or modifying the custom_fields attribute.

src/backend/langflow/template/frontend_node/base.py

@@ -1,3 +1,4 @@
+from collections import defaultdict
 import re
 from typing import List, Optional
 
@@ -47,7 +48,7 @@ class FrontendNode(BaseModel):
     name: str = ""
     display_name: str = ""
     documentation: str = ""
-    custom_fields: List[str] = []
+    custom_fields: defaultdict = defaultdict(list)
     output_types: List[str] = []
     field_formatters: FieldFormatters = Field(default_factory=FieldFormatters)