Only call NotifyBlockTip when the active chain changes

Previously, if `invalidateblock` was called on a block in a branch,
NotifyBlockTip would be called on that block's predecessor, creating an
incorrect `rpc/blockchain.cpp:latestblock` value.

Only call NotifyBlockTip if the chain being modified is activeChain.

Author: jamesob

src/validation.cpp

@@ -2731,7 +2731,11 @@ bool CChainState::InvalidateBlock(CValidationState& state, const CChainParams& c
     }
 
     InvalidChainFound(pindex);
-    uiInterface.NotifyBlockTip(IsInitialBlockDownload(), pindex->pprev);
+
+    // Only notify about a new block tip if the active chain was modified.
+    if (pindex_was_in_chain) {
+        uiInterface.NotifyBlockTip(IsInitialBlockDownload(), pindex->pprev);
+    }
     return true;
 }
 bool InvalidateBlock(CValidationState& state, const CChainParams& chainparams, CBlockIndex *pindex) {