Silence using uninitialized value

Hi.

Per Coverity.

Coverity has new report about tablecmds.c and tablespace.c

tablecmds.c:
CID 1608920: (#1 of 1): Uninitialized scalar variable (UNINIT)
6. uninit_use_in_call: Using uninitialized value *repl_val when calling
heap_modify_tuple.

CID 1608899: (#1 of 1): Uninitialized scalar variable (UNINIT)
16. uninit_use_in_call: Using uninitialized value *repl_val when calling
heap_modify_tuple.

tablespace.c:
CID 1608898: (#1 of 1): Uninitialized scalar variable (UNINIT)
6. uninit_use_in_call: Using uninitialized value *repl_val when calling
heap_modify_tuple.

I don't think that is a bug.
But really the uninitialized value is read here:
(src/backend/access/common/heaptuple.c )

3. read_value: Reading value replValues[attoff].
1242 values[attoff] = replValues[attoff];
1243 isnull[attoff] = replIsnull[attoff];
1244 }

There a common pattern in the source code:

value = (Datum) 0;
null = true;

So I believe it is worth changing to the standard used.

patch attached.

best regards,
Ranier Vilela