Fix handling of interconnect_address and parallel worker check in single-node setup

In InitializeParallelDSM(), interconnect_address may be NULL in a single-node
deployment. Avoid passing NULL to strcpy() by checking before use and fall back
to an empty string.

Also, in index_create_internal(), refine the condition for enabling parallel
index build. Instead of testing "ii_ParallelWorkers != -1", use the clearer and
correct check "ii_ParallelWorkers > 0".

Author: yjhjstz

src/backend/access/transam/parallel.c

@@ -379,7 +379,10 @@ InitializeParallelDSM(ParallelContext *pcxt)
 	/* CDB: should sync some global states to workes */
 	fps->cdb_aux_state.session_id = gp_session_id;
 	fps->cdb_aux_state.num_segments = numsegmentsFromQD;
-	strcpy(fps->cdb_aux_state.interconnect_address, interconnect_address);
+	if (interconnect_address)
+		strcpy(fps->cdb_aux_state.interconnect_address, interconnect_address);
+	else
+		fps->cdb_aux_state.interconnect_address[0] = '\0';
 	fps->cdb_aux_state.ic_htab_size = ic_htab_size;
 
 	/* We can skip the rest of this if we're not budgeting for any workers. */

src/backend/catalog/index.c

@@ -1388,7 +1388,7 @@ index_create_internal(Relation heapRelation,
 		 *
 		 * We should bring it back in the future.
 		 */
-		index_build(heapRelation, indexRelation, indexInfo, false, indexInfo->ii_ParallelWorkers != -1);
+		index_build(heapRelation, indexRelation, indexInfo, false, indexInfo->ii_ParallelWorkers > 0);
 	}
 
 	/*