Fix planner distributed table count

The check for a distributed hypertable was done after ht had been
changed to the compressed hypertable potentially leading to miscount
or even segfault when the cache lookup for the compressed hypertable
returned NULL.

(cherry picked from commit 727a027)

.unreleased/pr_6113

@@ -0,0 +1,3 @@
+Fixes: #6113 Fix planner distributed table count
+
+Thanks: @symbx for reporting a crash when selecting from empty hypertables

src/planner/planner.c

@@ -388,19 +388,18 @@ preprocess_query(Node *node, PreprocessQueryContext *context)
 							query->rowMarks == NIL && rte->inh)
 							rte_mark_for_expansion(rte);
 
+						if (hypertable_is_distributed(ht))
+						{
+							context->num_distributed_tables++;
+						}
+
 						if (TS_HYPERTABLE_HAS_COMPRESSION_TABLE(ht))
 						{
 							int compr_htid = ht->fd.compressed_hypertable_id;
 
 							/* Also warm the cache with the compressed
 							 * companion hypertable */
-							ht = ts_hypertable_cache_get_entry_by_id(hcache, compr_htid);
-							Assert(ht != NULL);
-						}
-
-						if (hypertable_is_distributed(ht))
-						{
-							context->num_distributed_tables++;
+							ts_hypertable_cache_get_entry_by_id(hcache, compr_htid);
 						}
 					}
 					else