Add double checks that WriteSerial and WriteMint succeed when process…

…ing an Elysium tx.

src/elysium/txprocessor.cpp

@@ -225,11 +225,17 @@ int TxProcessor::ProcessLelantusJoinSplit(const CMPTransaction& tx)
 
     // record serial and change
     for (auto const &s : serials) {
-        lelantusDb->WriteSerial(property, s, block, tx.getHash());
+        if (!lelantusDb->WriteSerial(property, s, block, tx.getHash())) {
+            PrintToLog("%s(): rejected: serial is duplicated\n", __func__);
+            return PKT_ERROR_LELANTUS - 907;
+        }
     }
 
     if (joinSplitMint.get_ptr() != nullptr) {
-        lelantusDb->WriteMint(property, joinSplitMint.get(), block);
+        if (!lelantusDb->WriteMint(property, joinSplitMint.get(), block)) {
+            PrintToLog("%s(): error writing mint\n", __func__);
+            // Accept the spend even if the mint is invalid. The mint will be unusable though.
+        }
     }
 
     assert(update_tally_map(tx.getReceiver(), property, spendAmount, BALANCE));