Package: emacs, cc-mode

From 'emacs -Q', eval the following:

(with-current-buffer (get-buffer-create "*test*")
  (erase-buffer)
  (insert "int main()\n{\n  \n}\n")
  (search-backward "\n}")
  (c-mode)
  (save-restriction
    (narrow-to-region (point) (point))
    (insert "foo")))

Gives the backtrace:

Debugger entered--Lisp error: (args-out-of-range 1 1)
  get-text-property(1 c-fl-syn-tab)
  c-clear-string-fences()
  #f(compiled-function () #<bytecode 0xbb39fd>)()
  c-after-change(16 19 0)
  insert("foo")
  (save-restriction (narrow-to-region (point) (point)) (insert "foo"))
  (save-current-buffer (set-buffer (get-buffer-create "*test*")) (erase-buffer) (insert "int main()\n{\n  \n}\n") (search-backward "\n}") (c-mode) (save-restriction (narrow-to-region (point) (point)) (insert "foo")))

This is a reduced test case from
https://github.com/joaotavora/eglot/issues/291.

I think the obvious fix is to extend the save-restriction just a bit
further to cover c-clear-string-fences, patch attached.