wcurl: fix missing argument crash for options

[arpitguptagithub]

This PR adds input validation checks before shift is called for the --curl-options and -o/-O/--output parameters.

Currently, if a user passes --curl-options or -o as the final argument without providing an actual value, the script blindly calls shift and then attempts to read ${1}. Because the script correctly uses set -eu, reading an unbound variable immediately crashes the program with an ugly shell interpreter error (unbound variable or parameter not set)....

instead of a helpful user-facing error.

This is a small patch .... which catches the missing parameter and gracefully reports it using the error() function.

small test is also added here testMissingArgumentError to tests.sh to explicitly verify behavior when an argument is omitted.

[sergiodj]

Thanks! There are some minor nits regarding the error message format. Let's get that fixed first :-).

[sergiodj]

Thank you!

[soliton-]

Note that -z checks for empty and not whether an argument was given so the error is misleading if an empty argument was given. The wcurl argument parsing loop is similarly broken by checking for empty instead of checking $#.