bug#16850: 24.3.50; lisp--local-variables raises error in comments and strings

[Dmitry Gutov]

1. Open an empty emacs-lisp-mode buffer.

2. Type `;; Thi' in it (`Thi' is an example of a prefix without known
completions).

3. Press `C-M-i', see "End of file during parsing" in the echo area.

This is a problem for Company, because it makes the company-capf
`candidates' action raise the error. Original report here:
https://github.com/company-mode/company-mode/issues/66

The error doesn't happen when the symbol before point does have some
completions. Not sure why, because `(lisp--local-variables)' raises the
error either way when evaluated directly.

In GNU Emacs 24.3.50.3 (x86_64-unknown-linux-gnu, GTK+ Version 3.8.6)
 of 2014-02-20 on axl
Repository revision: 116484 lekktu@gmail.com-20140219210406-y2s7lx244ojfl5on
Windowing system distributor `The X.Org Foundation', version 11.0.11405000
System Description:     Ubuntu 13.10