Address audit comments for LIP 0047 (#474)

* Addressed audit comments

proposals/lip-0047.md

@@ -7,7 +7,7 @@ Discussions-To: https://research.lisk.com/t/introduce-poa-module/288
 Status: Draft
 Type: Standards Track
 Created: 2021-04-29
-Updated: 2023-08-17
+Updated: 2023-09-04
 Requires: 0038, 0040, 0044
 ```
 
@@ -415,6 +415,8 @@ updateAuthorityValidatorParams = {
     "properties": {
         "newValidators": {
             "type": "array",
+            "minLength": 1,
+            "maxLength": MAX_NUM_VALIDATORS,
             "fieldNumber": 1,
             "items": {
                 "type": "object",
@@ -461,8 +463,6 @@ def verify(trs: Transaction) -> None:
     trsParams = decode(updateAuthorityValidatorParams, trs.params)
 
     newValidators = trsParams.newValidators
-    if length(newValidators) < 1 or length(newValidators) > MAX_NUM_VALIDATORS:
-        raise Exception()
     # Validator entries are ordered lexicographically with respect to address. Address is unique.
     for i in range(length(newValidators) - 1):
         if newValidators[i+1].address <= newValidators[i].address: # Lexicographical ordering.
@@ -471,8 +471,10 @@ def verify(trs: Transaction) -> None:
     for validator in newValidators:
         if validators(validator.address) is empty:
             raise Exception()
+        if validator.weight == 0:
+            raise Exception()
         totalWeight += validator.weight
-    if totalWeight > MAX_UINT64:
+    if totalWeight == 0 or totalWeight > MAX_UINT64:
         raise Exception()
 
     if trsParams.threshold < totalWeight // 3 + 1 or trsParams.threshold > totalWeight: