Merge pull request #589 from Nashatyrev/dev

Silently skip deposits with invalid proof in process_deposit

specs/core/0_beacon-chain.md

@@ -1254,13 +1254,16 @@ def process_deposit(state: BeaconState,
     Note that this function mutates ``state``.
     """
     # Validate the given `proof_of_possession`
-    assert validate_proof_of_possession(
+    proof_is_valid = validate_proof_of_possession(
         state,
         pubkey,
         proof_of_possession,
         withdrawal_credentials,
     )
 
+    if not proof_is_valid:
+        return
+
     validator_pubkeys = [v.pubkey for v in state.validator_registry]
 
     if pubkey not in validator_pubkeys: