change proof_is_valid to exit condition

specs/core/0_beacon-chain.md

@@ -1259,30 +1259,32 @@ def process_deposit(state: BeaconState,
         withdrawal_credentials,
     )
 
-    if proof_is_valid:
-        validator_pubkeys = [v.pubkey for v in state.validator_registry]
-    
-        if pubkey not in validator_pubkeys:
-            # Add new validator
-            validator = Validator(
-                pubkey=pubkey,
-                withdrawal_credentials=withdrawal_credentials,
-                activation_epoch=FAR_FUTURE_EPOCH,
-                exit_epoch=FAR_FUTURE_EPOCH,
-                withdrawal_epoch=FAR_FUTURE_EPOCH,
-                penalized_epoch=FAR_FUTURE_EPOCH,
-                status_flags=0,
-            )
-    
-            # Note: In phase 2 registry indices that have been withdrawn for a long time will be recycled.
-            state.validator_registry.append(validator)
-            state.validator_balances.append(amount)
-        else:
-            # Increase balance by deposit amount
-            index = validator_pubkeys.index(pubkey)
-            assert state.validator_registry[index].withdrawal_credentials == withdrawal_credentials
-    
-            state.validator_balances[index] += amount
+    if not proof_is_valid:
+        return
+
+    validator_pubkeys = [v.pubkey for v in state.validator_registry]
+
+    if pubkey not in validator_pubkeys:
+        # Add new validator
+        validator = Validator(
+            pubkey=pubkey,
+            withdrawal_credentials=withdrawal_credentials,
+            activation_epoch=FAR_FUTURE_EPOCH,
+            exit_epoch=FAR_FUTURE_EPOCH,
+            withdrawal_epoch=FAR_FUTURE_EPOCH,
+            penalized_epoch=FAR_FUTURE_EPOCH,
+            status_flags=0,
+        )
+
+        # Note: In phase 2 registry indices that have been withdrawn for a long time will be recycled.
+        state.validator_registry.append(validator)
+        state.validator_balances.append(amount)
+    else:
+        # Increase balance by deposit amount
+        index = validator_pubkeys.index(pubkey)
+        assert state.validator_registry[index].withdrawal_credentials == withdrawal_credentials
+
+        state.validator_balances[index] += amount
 ```
 
 ### Routines for updating validator status