Initialize the components of this class. Otherwise GCC thinks that Array may be

Initialize the components of this class.  Otherwise GCC thinks that Array may be
used uninitialized, since it fails to understand that Array is only used when
SingleValue is not, and outputs a warning.  It also seems generally safer given
that the constructor is non-trivial and has plenty of early exits.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173242 91177308-0d34-0410-b5e6-96231b3b80d8