Update app.py

app.py

@@ -165,7 +165,7 @@ def quote_year_choices():
 
 def quote_month_choices(year=None):
     """
-    Returns a sorted list of valid month strings for a given year, or [''] if none.
+    Returns a sorted list of valid month strings for a given year, always at least [''].
     """
     df = get_quotes_df()
     if (
@@ -177,8 +177,9 @@ def quote_month_choices(year=None):
         subset = df[df["Year"].astype(str) == str(year)]
         try:
             months = pd.to_numeric(subset["Month"], errors="coerce").dropna().astype(int)
-            months = sorted({str(m) for m in months if 1 <= m <= 12})
-            return months if months else [""]
+            months = [str(m) for m in months if 1 <= m <= 12]
+            months = sorted(set(months))
+            return [""] + months if months else [""]
         except Exception:
             return [""]
     return [""]