[PATCH] libdw: Fix crashing on illegal/zero Dwarf_Die.

[Mark Wielaard]

On Fri, 2018-05-11 at 12:49 +0200, Mark Wielaard wrote:
> In some cases we create an illegal Dwarf_Die by clearing all fields.
> The idea is that dwarf_tag () on such a Dwarf_Die will return
> DW_TAG_invalid, to indicate that the Dwarf_Die is unusable (and other
> functions will also return errors).  But when "reconstructing" the
> Dwarf_Die addr we might use the cu before realizing the Dwarf_Die is
> invalid.  Fix this with an explicit NULL check and add a testcase.

Pushed to master.