Fix UI error crash when clearing form by preventing full dataset load in get_udise_choices

hf_reader.py

@@ -351,6 +351,9 @@ def search_udise(udise_code: str, marksheet_name: str = "") -> list[dict]:
 
 def get_udise_choices(state: str, district: str, block: str, village: str = None) -> list[str]:
     """Returns a list of 'UDISE - School Name' for the given location filter."""
+    if not state:
+        return []
+        
     _ensure_loaded()
     
     dfs_to_process = []