fix(options): crash on ":let &l:autoread = v:true" #41158

Problem:
Assigning to the local value of a global-local boolean option
('autoread', 'autocomplete', 'fsync') aborts:

    Assertion failed: (curval.type == newval.type), function
    ex_let_option, file vars.c, line 1408.

    ex_let_one
    ex_let_vars
    ex_let
    execute_cmd0
    do_cmdline
    call_user_func
    ...
    eval_map_expr
    vgetorpeek
    vgetc
    state_enter
    main

A global-local option may have local value `kObjectTypeUnset`, but
`ex_let_option()` guards only `kObjectTypeNil`.

Solution:
When curval is Unset, resolve it to the inherited global value.

0 files changed, 0 insertions, 0 deletions