[Proposal] Filtering when an empty command is passed

[woung717]

In the current implementation, an exception prevention for empty string("") commands is required.
If an empty string is passed, the shlex function returns an empty list, causing an unpacking error when trying to unpack into one or more return variables. (at L63)

pr-agent/pr_agent/agent/pr_agent.py

Lines 54 to 66 in c4dc263

	async def handle_request(self, pr_url, request, notify=None) -> bool:
	# First, apply repo specific settings if exists
	apply_repo_settings(pr_url)
	# Then, apply user specific settings if exists
	if isinstance(request, str):
	request = request.replace("'", "\\'")
	lexer = shlex.shlex(request, posix=True)
	lexer.whitespace_split = True
	action, *args = list(lexer)
	else:
	action, *args = request

This can happen if an empty string is set in .pr_agent.toml like this

pr_commands = [ "" ]

Thank you for developing this amazing project.