Issue:

The 'Item_func_spatial_rel::spatial_rel' member was changed from WITHIN to
CONTAINS during execution and was not changed back in one of the rare
function return path, causing the function item to become WITHIN when
the query is executed next time, and since the optimized query plan of
the stored program is cached, the same WITHIN function item is reused and
thus MySQL returns different results starting from the 2nd run.

Fix:

Make sure 'Item_func_spatial_rel::spatial_rel' is always correctly restored
if temporarily changed to another value.