Problem: Strange error with type for matchfuzzy() "camelcase".
Solution: Show the error "Invalid value for argument camelcase" instead
of "Invalid argument: camelcase" (zeertzjq).
Note that using tv_get_string() will lead to confusion, as when the
value cannot be converted to a string tv_get_string() will also give an
error about that, but "camelcase" takes a boolean, not a string. Also
don't use tv_get_string() for the "limit" argument above.
closes: vim/vim#16926c4815c157b
797195e0ea