rpc: Fix for segfault if combinepsbt called with empty inputs

src/rpc/rawtransaction.cpp

@@ -1514,6 +1514,9 @@ UniValue combinepsbt(const JSONRPCRequest& request)
     // Unserialize the transactions
     std::vector<PartiallySignedTransaction> psbtxs;
     UniValue txs = request.params[0].get_array();
+    if (txs.empty()) {
+        throw JSONRPCError(RPC_INVALID_PARAMETER, "Parameter 'txs' cannot be empty");
+    }
     for (unsigned int i = 0; i < txs.size(); ++i) {
         PartiallySignedTransaction psbtx;
         std::string error;