[Qt] Console: allow empty arguments

[jonasschnelli]

Should fix #9210 and re-allow empty arguments like command '' <more arg...> or command "" <more args...>.

[luke-jr]

Maybe add a unit test to check this case?

[luke-jr]

This doesn't appear to actually fix the problem at all: luke-jr/bitcoin@3710cf3

[jonasschnelli]

Added @luke-jr's unit test, added some more fixes.

[luke-jr]

Here's a few more, including one that fails:

    RPCConsole::RPCExecuteCommandLine(result, "rpcNestedTest(abc,,abc)");
    QVERIFY(result == "[\"abc\",\"\",\"abc\"]");
    RPCConsole::RPCExecuteCommandLine(result, "rpcNestedTest(abc,,)");  // this one fails
    QVERIFY(result == "[\"abc\",\"\",\"\"]");
    RPCConsole::RPCExecuteCommandLine(result, "rpcNestedTest(abc )");
    QVERIFY(result == "[\"abc\"]");
    RPCConsole::RPCExecuteCommandLine(result, "rpcNestedTest( abc)");
    QVERIFY(result == "[\"abc\"]");

[jonasschnelli]

Added more rules and tests.
Now, empty arguments are no longer supported when using the comma-syntax.
Examples

• [NOK] command <arg0>,,<arg2>
• [OK] command <arg0>,"",<arg2>
• [NOK] command(<arg0>,,<arg2>)
• [NOK] command(<arg0>,)
• [OK] command <arg0> "" <arg2>
• [OK] command( <arg0> , <arg2> )

[laanwj]

Now, empty arguments are no longer supported when using the comma-syntax.

Makes sense, I think.
Thanks for adding tests :)
code-review-ACK 413ce40