[patch] libstdc++/65352 fix ubsan errors in std::array<T, 0>

[Jonathan Wakely]

Unsurprisingly ubsan doesn't like referencing a null pointer.

With this change __array_traits::_S_ref is only used to access an
element, which is invalid for std::array<T, 0> anyway.

Tested powerpc64le-linux, committed to trunk.

-------------- next part --------------
A non-text attachment was scrubbed...
Name: patch.txt
Type: text/x-patch
Size: 3069 bytes
Desc: not available
URL: <http://gcc.gnu.org/pipermail/libstdc++/attachments/20150528/9d4b6203/attachment.bin>