[BUG] _gnu_generic completer produces broken output

[Marlon Richert <marlon.richert@xxxxxxxxx>]

Fails with both 5.8 and the current master branch (commit d9e5ef020).
Looks like the same bug as workers 48091.

% autoload compinit && compinit
% compdef _gnu_generic -command- -P '*'
% pip3 -
--cache-dir
--cert
--client-cert
--disable-pip-version-check
--exists-action
--help
--isolated
--log
--no-cache-dir
--no-color
--proxy
--quiet
--retries
--timeout
--trusted-host
--verbose
--version





-h





-q



-v
-V
-- Store the cache data in <dir>.
-- Path to alternate CA bundle.
-- Path to SSL client certificate, a single file
-- Don't periodically check PyPI to determine
-- Default action when a path already exists-
-- Show help.
-- Run pip in an isolated mode, ignoring
-- Path to a verbose appending log.
-- Disable the cache.
-- Suppress colored output
-- Specify a proxy in the form
-- Give less output. Option is additive, and can be
-- Maximum number of retries each connection should
-- Set the socket timeout (default 15 seconds).
-- Mark this host as trusted, even though it does
-- Give more output. Option is additive, and can be
-- Show version and exit.
--cache-dir
--cert
--client-cert
--disable-pip-version-check
--exists-action
--help
--isolated
--log
--no-cache-dir
--no-color
--proxy
--quiet
--retries
--timeout
--trusted-host
--verbose
--version





-h





-q



-v
-V
-- Store the cache data in <dir>.
-- Path to alternate CA bundle.
-- Path to SSL client certificate, a single file
-- Don't periodically check PyPI to determine
-- Default action when a path already exists-
-- Show help.
-- Run pip in an isolated mode, ignoring
-- Path to a verbose appending log.
-- Disable the cache.
-- Suppress colored output
-- Specify a proxy in the form
-- Give less output. Option is additive, and can be
-- Maximum number of retries each connection should
-- Set the socket timeout (default 15 seconds).
-- Mark this host as trusted, even though it does
-- Give more output. Option is additive, and can be
-- Show version and exit.
--cache-dir
--cert
--client-cert
--disable-pip-version-check
--exists-action
--help
--isolated
--log
--no-cache-dir
--no-color
--proxy
--quiet
--retries
--timeout
--trusted-host
--verbose
--version





-h





-q



-v
-V
-- Store the cache data in <dir>.
-- Path to alternate CA bundle.
-- Path to SSL client certificate, a single file
-- Don't periodically check PyPI to determine
-- Default action when a path already exists-
-- Show help.
-- Run pip in an isolated mode, ignoring
-- Path to a verbose appending log.
-- Disable the cache.
-- Suppress colored output
-- Specify a proxy in the form
-- Give less output. Option is additive, and can be
-- Maximum number of retries each connection should
-- Set the socket timeout (default 15 seconds).
-- Mark this host as trusted, even though it does
-- Give more output. Option is additive, and can be
-- Show version and exit.
% pip3 -