of its arguments was evaluated to NULL, while the predicate
LOCATE(str,NULL) IS NULL erroneously was evaluated to FALSE.

This happened because the Item_func_locate::fix_length_and_dec
method by mistake set the value of the maybe_null flag for 
the function item to 0. In consequence of this the function 
was considered as the one that could not ever return NULL.


mysql-test/r/func_str.result:
  Added a test case for bug #27932.
mysql-test/t/func_str.test:
  Added a test case for bug #27932.