[refactor] remove access to mapTx from policy/rbf.cpp

src/policy/rbf.cpp

@@ -12,6 +12,7 @@
 #include <tinyformat.h>
 #include <txmempool.h>
 #include <uint256.h>
+#include <util/check.h>
 #include <util/moneystr.h>
 #include <util/rbf.h>
 
@@ -35,7 +36,7 @@ RBFTransactionState IsRBFOptIn(const CTransaction& tx, const CTxMemPool& pool)
 
     // If all the inputs have nSequence >= maxint-1, it still might be
     // signaled for RBF if any unconfirmed parents have signaled.
-    const CTxMemPoolEntry entry{*pool.mapTx.find(tx.GetHash())};
+    const auto& entry{*Assert(pool.GetEntry(tx.GetHash()))};
     auto ancestors{pool.AssumeCalculateMemPoolAncestors(__func__, entry, CTxMemPool::Limits::NoLimits(),
                                                         /*fSearchForParents=*/false)};