Fix bug in parsing HSTS certificates file

Bug: 817979
Change-Id: I0a7ac6811306123f1bd55ef2def0f00283116b55
Reviewed-on: https://chromium-review.googlesource.com/944516Reviewed-by: Eric Lawrence <elawrence@chromium.org>
Reviewed-by: Chris Palmer <palmer@chromium.org>
Commit-Queue: Nick Harper <nharper@chromium.org>
Cr-Commit-Position: refs/heads/master@{#540361}

net/tools/transport_security_state_generator/input_file_parsers.cc

@@ -205,7 +205,7 @@ bool ParseCertificatesFile(base::StringPiece certs_input, Pinsets* pinsets) {
 
   for (const base::StringPiece& line : SplitStringPiece(
            certs_input, "\n", base::KEEP_WHITESPACE, base::SPLIT_WANT_ALL)) {
-    if (line[0] == '#') {
+    if (!line.empty() && line[0] == '#') {
       continue;
     }