Don't crash if a declarator in a friend decl doesn't have a name.

There was already an explicit check for that for the first decl.  Move that
to a different place so that it's called for the following decls too.  Also
don't randomly set the BitfieldSize ExprResult to true (this sets a pointer to
true internally).

Found by SLi's bot.

llvm-svn: 226306