Don't clear weights if unsuccessful sync

src/chain_data.py

@@ -84,7 +84,6 @@ def query_subtensor(storage_keys: list[StorageKey], block: int) -> list:
 
 
 def fetch_weights(block: int):
-    WEIGHTS_BY_MINER.clear()
     storage_keys: list[StorageKey] = []
     for hotkey, neuron in get_neurons().items():
         if not neuron.validator_permit: continue
@@ -95,6 +94,7 @@ def fetch_weights(block: int):
         ))
 
     weights = query_subtensor(storage_keys, block)
+    WEIGHTS_BY_MINER.clear()
 
     for hotkey, neuron in get_neurons().items():
         for storage, validator_weights in weights: