quipper: Don't call fclose() on null FILE pointer

The behavior is undefined. Check for it in FileReader.

Also replaced some fopen/fclose file reads with FileReader.

BUG=chromium:649242
TEST=build successfully

Change-Id: I111cb3263abdfbc6f232517f47f296646e3f60c3
Previous-Reviewed-on: https://chromium-review.googlesource.com/394231
(cherry picked from commit f9583eeb3849b1616d9e6af28222608ff0d665a6)
Reviewed-on: https://chromium-review.googlesource.com/394231
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
Reviewed-by: Chong Jiang <chongjiang@chromium.org>
Reviewed-by: Simon Que <sque@chromium.org>
Tested-by: Simon Que <sque@chromium.org>
3 files changed