blockchain: return error when requesting non existent output

avoids RPC thread dying, causing the wallet to timeout

src/cryptonote_core/blockchain.cpp

@@ -1941,14 +1941,21 @@ bool Blockchain::get_outs(const COMMAND_RPC_GET_OUTPUTS_BIN::request& req, COMMA
 
   res.outs.clear();
   res.outs.reserve(req.outputs.size());
-  for (const auto &i: req.outputs)
+  try
   {
-    // get tx_hash, tx_out_index from DB
-    const output_data_t od = m_db->get_output_key(i.amount, i.index);
-    tx_out_index toi = m_db->get_output_tx_and_index(i.amount, i.index);
-    bool unlocked = is_tx_spendtime_unlocked(m_db->get_tx_unlock_time(toi.first));
+    for (const auto &i: req.outputs)
+    {
+      // get tx_hash, tx_out_index from DB
+      const output_data_t od = m_db->get_output_key(i.amount, i.index);
+      tx_out_index toi = m_db->get_output_tx_and_index(i.amount, i.index);
+      bool unlocked = is_tx_spendtime_unlocked(m_db->get_tx_unlock_time(toi.first));
 
-    res.outs.push_back({od.pubkey, od.commitment, unlocked, od.height, toi.first});
+      res.outs.push_back({od.pubkey, od.commitment, unlocked, od.height, toi.first});
+    }
+  }
+  catch (const std::exception &e)
+  {
+    return false;
   }
   return true;
 }