Merge bitcoin/bitcoin#24227: Fix unsigned integer overflow in LoadMempool

fadcd03139 Fix unsigned integer overflow in LoadMempool (MarcoFalke)

Pull request description:

  It doesn't seem ideal to have an integer sanitizer enabled, but then disable it for the whole validation.cpp file.

  This removes one of the two violations.

  This should be a refactor.

ACKs for top commit:
  prayank23:
    Code Review ACK fadcd03139

Tree-SHA512: 9fb2f3d49008a59cd45b7c17be0c88c04e61183197c11c8176865af5532c8d0c940db49a351dd0fc75e1d7fd8678c3b816d34cfca170dc6b9cf8f37fdf1c8cae

src/validation.cpp

@@ -4493,7 +4493,8 @@ bool LoadMempool(CTxMemPool& pool, CChainState& active_chainstate, FopenFn mocka
         }
         uint64_t num;
         file >> num;
-        while (num--) {
+        while (num) {
+            --num;
             CTransactionRef tx;
             int64_t nTime;
             int64_t nFeeDelta;