Update parse csv string functions with none check

app.py

@@ -43,11 +43,15 @@ dspy.settings.configure(lm=model)
 # Utils
 def parse_CSV_string(csv_string):
   # Parses a CSV string into a list
+  if not csv_string:
+    return []
   return list(map(str.strip, csv_string.split(',')))
 
 
 def parse_CSV_string_to_unique(csv_string):
   # Parses a CSV string into a unique list
+  if not csv_string:
+    return []
   return list(set(map(str.lower, map(str.strip, csv_string.split(',')))))
 
 def parse_list_of_CSV_strings(list_of_csv_strings):