A call to TYPE_TARGET_TYPE was being done without checking if the type
does have a target type. This was introduced by my commit:
82c48ac732edb0155288a93ef3dd39625ff2d2e1

The attached patch fixes it. This probably qualifies as an obvious
fix, but just in case.

 2014-10-16  Siva Chandra Reddy  <sivachandra@google.com>

        * gnu-v3-abi.c (gnuv3_pass_by_reference): Call TYPE_TARGET_TYPE
        on the arg type of a constructor only if it is of reference type.