pgsql: Fix possibly-uninitialized-variable warning from commit9556aa01

Fix possibly-uninitialized-variable warning from commit 9556aa01c.

Heikki's compiler doesn't complain about end_ptr, apparently,
but mine does.

In passing, I failed to resist the temptation to remove the
no-longer-used fldnum variable, and relocate chunk_len's
declaration to a narrower scope.

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/6119060d01ab2dfb9e2c1c101595f2de7890965d

Modified Files
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src/backend/utils/adt/varlena.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)