eval: fix assertion failure in garbage collection (#12436)

* eval: fix assertion failure in garbage collection

fixes #12387, #12430

Lists with CopyID+1 linked only from previous_funccal may be removed in
the garbage collection. Therefore, the terms of the assertions are not
correct. This can be confirmed by the following (The l:x with CopyID+1 of
the first function call needs to be removed by garbage collection):

func! s:f()
  let l:x = [1]
  let g:x = l:
endfunc

for _ in range(2)
  call s:f()
endfor
call garbagecollect()
" press any key

* test: add test for #12387, #12430

0 files changed, 0 insertions, 0 deletions