pgsql: Fix overly-strict assertions in spgtextproc.c.

Fix overly-strict assertions in spgtextproc.c.

spg_text_inner_consistent is capable of reconstructing an empty string
to pass down to the next index level; this happens if we have an empty
string coming in, no prefix, and a dummy node label.  (In practice, what
is needed to trigger that is insertion of a whole bunch of empty-string
values.)  Then, we will arrive at the next level with in->level == 0
and a non-NULL (but zero length) in->reconstructedValue, which is valid
but the Assert tests weren't expecting it.

Per report from Andreas Seltenreich.  This has no impact in non-Assert
builds, so should not be a problem in production, but back-patch to
all affected branches anyway.

In passing, remove a couple of useless variable initializations and
shorten the code by not duplicating DatumGetPointer() calls.

Branch
------
REL9_3_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/2917155d5805f16584e323b8764fd01b4023361a

Modified Files
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src/backend/access/spgist/spgtextproc.c |   14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)