Avoid a write to NULL in ReadFieldBinary

what happens is that we use vector_as_array(&data) which returns null if data is empty, but we don't check |size| whichcan be 0 so data.resize(size) still an empty vector.

This is currently happening for browser_tests.exe in the waterfall.

There might be a better fix but lots of tests are having exceptions so I want to stop that.

TBR=mnissler
BUG=none
TEST=logs are clean

Review URL: https://codereview.chromium.org/23961004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@222177 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/policy/preg_parser_win.cc

@@ -66,6 +66,8 @@ bool ReadFieldBinary(const uint8** cursor,
                      const uint8* end,
                      int size,
                      uint8* data) {
+  if (!size)
+    return false;
   const uint8* field_end = *cursor + size;
   if (field_end > end)
     return false;