MDEV-13226 Server crashes when tmpdir runs out of space

There was a missing test in CTE handling if creating a temporary table
failed (in this case as a result of out of space). This caused a table
handler to be used even if it was not allocated.

sql/sql_select.cc

@@ -26304,7 +26304,8 @@ AGGR_OP::put_record(bool end_of_records)
 {
   // Lasy tmp table creation/initialization
   if (!join_tab->table->file->inited)
-    prepare_tmp_table();
+    if (prepare_tmp_table())
+      return NESTED_LOOP_ERROR;
   enum_nested_loop_state rc= (*write_func)(join_tab->join, join_tab,
                                            end_of_records);
   return rc;