Improve readability of DecodeBase58Check(...)

src/base58.cpp

@@ -136,7 +136,7 @@ bool DecodeBase58Check(const char* psz, std::vector<unsigned char>& vchRet)
     }
     // re-calculate the checksum, ensure it matches the included 4-byte checksum
     uint256 hash = Hash(vchRet.begin(), vchRet.end() - 4);
-    if (memcmp(&hash, &vchRet.end()[-4], 4) != 0) {
+    if (memcmp(&hash, &vchRet[vchRet.size() - 4], 4) != 0) {
         vchRet.clear();
         return false;
     }