fix: require v20 fork activated for reallocation block reward to credit pool

It is appliable for test networks which could have custom height of forks

Author: knst

src/evo/creditpool.cpp

@@ -243,7 +243,7 @@ CCreditPoolDiff::CCreditPoolDiff(CCreditPool starter, const CBlockIndex* pindexP
     assert(pindexPrev);
 
     if (DeploymentActiveAfter(pindexPrev, consensusParams, Consensus::DEPLOYMENT_MN_RR)) {
-        // We consider V20 active if mn_rr is active
+        // No credit pool exists before V20.
         platformReward = PlatformShare(GetMasternodePayment(pindexPrev->nHeight + 1, blockSubsidy, /*fV20Active=*/ true));
     }
 }

src/masternode/payments.cpp

@@ -41,7 +41,9 @@ CAmount PlatformShare(const CAmount reward)
     bool fV20Active = DeploymentActiveAfter(pindexPrev, m_consensus_params, Consensus::DEPLOYMENT_V20);
     CAmount masternodeReward = GetMasternodePayment(nBlockHeight, blockSubsidy + feeReward, fV20Active);
 
-    if (DeploymentActiveAfter(pindexPrev, m_consensus_params, Consensus::DEPLOYMENT_MN_RR)) {
+    // Credit Pool doesn't exist before V20. If any part of reward will re-allocated to credit pool before v20
+    // activation these fund will be just permanently lost. Applyable for devnets, regtest, testnet
+    if (fV20Active && DeploymentActiveAfter(pindexPrev, m_consensus_params, Consensus::DEPLOYMENT_MN_RR)) {
         CAmount masternodeSubsidyReward = GetMasternodePayment(nBlockHeight, blockSubsidy, fV20Active);
         const CAmount platformReward = PlatformShare(masternodeSubsidyReward);
         masternodeReward -= platformReward;