maint: Reduce number of reverse gotos

Although the compiler doesn't care about it, having later code jump
backwards to an earlier common error handling block, particularly when
that earlier block is nested inside a conditional, is unusual compared
to programming paradigms where exception handling occurs later in the
function.  Relocate the common error handling block to be at the end
of the function, outside conditional nesting.  No semantic change.

Suggested-by: Laszlo Ersek <lersek@redhat.com>