Merge bitcoin-core#446: RPCConsole: Throw when overflowing size_t type for array indices

faa5e17 RPCConsole: Throw when overflowing size_t type for array indices (MarcoFalke)

Pull request description:

  To test:

  -> `getblock(getbestblockhash(), 1)[tx][22222222222222222222222222222]`

  Before:

  <- `868693731dea69a197c13c2cfaa41c9f78fcdeb8ab8e9f8cdf2c9025147ee7d1` (hash of the coinbase tx)

  After:

  <- `Error: Invalid result query`

ACKs for top commit:
  jarolrod:
    ACK faa5e17
  shaavan:
    ACK faa5e17

Tree-SHA512: ddff39aae1c15db45928b110a9f1c42eadc5404cdfa89d67ccffc4c6af24091967d43c068ce9e0c1b863cfc4eb5b4f12373a73756a9474f8294e8a44aabc28d8

Author: MarcoFalke

src/qt/rpcconsole.cpp

@@ -247,10 +247,11 @@ bool RPCConsole::RPCParseCommandLine(interfaces::Node* node, std::string &strRes
                                 UniValue subelement;
                                 if (lastResult.isArray())
                                 {
-                                    for(char argch: curarg)
-                                        if (!IsDigit(argch))
-                                            throw std::runtime_error("Invalid result query");
-                                    subelement = lastResult[LocaleIndependentAtoi<int>(curarg)];
+                                    const auto parsed{ToIntegral<size_t>(curarg)};
+                                    if (!parsed) {
+                                        throw std::runtime_error("Invalid result query");
+                                    }
+                                    subelement = lastResult[parsed.value()];
                                 }
                                 else if (lastResult.isObject())
                                     subelement = find_value(lastResult, curarg);