Fix empty Redis command array parsing

[wwbmmm]

What problem does this PR solve?

Issue Number: null

Problem Summary:

The Redis command parser accepted an empty RESP array as the start of a command
and kept parsing subsequent bulk strings as array elements. Since an empty array
has no command name or arguments, this input should be rejected by the parser.

What is changed and the side effects?

Changed:

• Reject empty RESP command arrays in RedisCommandParser.
• Replace the internal array index CHECK with an explicit parse error before
  writing parsed bulk strings into the argument vector.
• Add a parser regression test for empty RESP arrays followed by bulk strings.

Side effects:

• Performance effects: None expected.

• Breaking backward compatibility: Empty RESP arrays are now rejected as invalid
  Redis commands.

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Check List:

• Please make sure your changes are compilable.
• When providing us with a new feature, it is best to add related tests.
• Please follow Contributor Covenant Code of Conduct.

[chenBright]

LGTM