Merge #11238: Add assertions before potential null deferences

c00199244 Fix potential null dereferences (MeshCollider)

Pull request description:

  Picked up by the static analyzer [Facebook Infer](http://fbinfer.com/) which I was playing around with for another research project. Just adding some asserts before dereferencing potentially null pointers.

Tree-SHA512: 9c01dab2d21bce75c7c7ef867236654ab538318a1fb39f96f09cdd2382a05be1a6b2db0a1169a94168864e82ffeae0686a383db6eba799742bdd89c37ac74397

src/rpc/blockchain.cpp

@@ -814,6 +814,7 @@ static void ApplyStats(CCoinsStats &stats, CHashWriter& ss, const uint256& hash,
 static bool GetUTXOStats(CCoinsView *view, CCoinsStats &stats)
 {
     std::unique_ptr<CCoinsViewCursor> pcursor(view->Cursor());
+    assert(pcursor);
 
     CHashWriter ss(SER_GETHASH, PROTOCOL_VERSION);
     stats.hashBlock = pcursor->GetBestBlock();
@@ -1517,6 +1518,8 @@ UniValue getchaintxstats(const JSONRPCRequest& request)
             pindex = chainActive.Tip();
         }
     }
+    
+    assert(pindex != nullptr);
 
     if (blockcount < 1 || blockcount >= pindex->nHeight) {
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid block count: should be between 1 and the block's height");