blockchain: return error when requesting non existent output

avoids RPC thread dying, causing the wallet to timeout

src/cryptonote_core/blockchain.cpp

@@ -1941,6 +1941,8 @@ bool Blockchain::get_outs(const COMMAND_RPC_GET_OUTPUTS_BIN::request& req, COMMA
 
   res.outs.clear();
   res.outs.reserve(req.outputs.size());
+  try
+  {
     for (const auto &i: req.outputs)
     {
       // get tx_hash, tx_out_index from DB
@@ -1950,6 +1952,11 @@ bool Blockchain::get_outs(const COMMAND_RPC_GET_OUTPUTS_BIN::request& req, COMMA
 
       res.outs.push_back({od.pubkey, od.commitment, unlocked, od.height, toi.first});
     }
+  }
+  catch (const std::exception &e)
+  {
+    return false;
+  }
   return true;
 }
 //------------------------------------------------------------------