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 <[email protected]> Reviewed-by: Chong Jiang <[email protected]> Reviewed-by: Simon Que <[email protected]> Tested-by: Simon Que <[email protected]>