Gcc11 warning on patches15_18

[pashkinelfe]

planner.c: In function ‘subquery_planner’:
planner.c:2290:41: warning: ‘refType’ may be used uninitialized [-Wmaybe-uninitialized]
 2290 |                 newrc->allRefTypes = (1 << refType);
      |                                      ~~~^~~~~~~~~~~